Minor strategies
There are numerous minor strategies, used in ruling a vast number of nobles who are extremely wealthy and powerful: ie, rule worldwide fiefs.
In general, these tactics are perfectly usable in the OTU. They are just 'biggie-sized' and tailored to handle a bunch of dominance-hungry individuals, instead of balancing corporations and system populations.
* Help the People
The Emperor continually spends a ton of money on "bread and circuses." Well, not bread: the Imperium is incapable of building a stable, Imperium-wide socialist network. (Early Sector- and Subsector-wide experiments ended in tears within a century, IMTU).
But it is certainly possible to spend money on entertainment and various festivals. The Emperor sets the pace with the Imperial Games, held once every decade. [I *believe* this is actually canon!]
IMTU, the Emperor also spends a LOT of money on ceebrating the Imperial New Year and the Emperor's Birthday. Various lesser festivals - like Navy Day - also consume a chunk of his money (and, more importantly, his time.) A large wad of cash goes into cultural festivals, generous gifts to impoverished (but highly loyal) Imperial subjects, donations to important interstellar religions, funding conferences for various scientific guilds and organizations, relief for Imperial military veterans (above and beyond the offical Imperial health package), and on and on and ON.
And - vastly more important than the cast outflow - is the amount of time devoured by all these ribbon-cutting ceremonies. Nobles who are busy kissing babies can't spend the time scheming how to replace the local capital ship captains (who are all nobles or knights in their own right) with political allies....
The nobility are under extremely strong social pressure to spend a good chunk of their wealth and time every year on "society". On some worlds, Noble houses have been deposed and exiled for failing to "share the wealth" often enough.
* Serious capital investment
The Imperium encourages her noblity to spend a lot of capital on long-term projects, usually terraforming and tech uplift for their worlds. There are great rewards for this, as the noble who funds these endeavors are allowed to keep the glorious profits (excluding the usual Imperial tax, naturally.) However, money tied up in colonizing the asteroid belt cannot be used to hire "the baddest mercenaries in 20 parsecs."
* Prestige
"Keeping up with House Smith" is a major part of many Noble's lifestyle. Giving the most costly and elegant gifts, having each estate redecorated by the local Michelangelo, having your own 10 sq km. terraformed "Garden" on an asteroid, setting up a private space station at the edge of the local solar system, having your children run "the Grand Imperial Tour" to all the sector capitals (and Sylea, of course!), etc, etc, etc...
* War
Also a major source of Noble prestige is warfare. Due to strong Imperial patronage (IMTU), a lot of this warfare is in the form of bloody 'games': gladiator contests, gunpower-free fights (from sword duels to armies with short swords and catapults), Mechwarrior contests, Zero-G spikedancing, etc.
Despite these substitutes, there are still real wars fought within the Imperium. The Emperor tries to restrict warfare to limit wealth destruction. However, so long as Imperial rule and facilites are not threatened, real restructions on war is left for the subsector Duke to enforce.
* Decadence
In IMTU, Imperial authority unoffically discourages overmuch spending on sensual pleasures: a few high-class, purpose-bred prostitutes should be enough for anyone. However, SOME Nobles (who shall remain nameless, but can rank as high as an Imperial Prince) just don't know when to say 'enough'. Such individuals are encouraged to keep their activities on their own worlds, under wraps so the Imperium as a whole is not shamed by the actions of a few insanely wealthy individuals.
*****************************
Summary:
In a "worldwide fief" environment, the centre of wealth shifts from the megacorps to individual noble houses: military power also undergoes a major shift, from planetary governments and megacorps to noble houses.
(Regarding megacorps: because the Noble shareholders dominate and run the megacorps, instead of non-noble corporate officers, megacoroprations are better understood not as non-governmental businesses, but as alliances of noble-run businesses and interests. They are more fragile, as the megacorp is as fragmented and feudal as the Imperium itself, instead of being a conformist whole under a single corporate identity.)
Now, this has a variety of effects. Imperial stability is weakened to the extent that megacorp culture is broken, replaced by the culture of various noble houses. Imperial AUTHORITY is greatly strengthened, as the restraing forces of sovereign planetary governments no longer exist. The Imperium no longer governs just "the space between the stars", but directly governs the worlds as well.
All armies and all navies are under the rule of Imperial nobles, without exception.
While megacorp culture is largely gone, Vilani, Sylean, and Solomani culture remains unchanged. Networks of allied noble houses will create their own distinct culture, and fill in the vacumm left behind. (The largest and most influencial networks will be Vilani, of course.)
People matter than systems or organizations. Patronage takes on larger-than-life importance, when a single man's will can shift awesome amounts of money and manpower.
There will be greater highs and deeper lows among Imperial worlds. A single Noble genius can gain lasting fame: a single Noble fool can cause lasting devastation. The differing lifespans and cultures of Vilani nobles (200 - 300 years) and Solomani nobles (70 - 120 years) will have huge consequences over time. The values of a Noble house will tend to be imprinted on the worlds they govern.
As the Imperium is more fragmented, there is less likelihood of a widespread rebellion. On the other hand, small-scale rebels can go on and on and on, for centuries. The overall Imperial environment will be more chaotic. However, very few problems will be able to grow past the Subsector level: it is possible that even the (First) Ilelish Rebellion would be basically impossible in this senario.
Because Hostile (and possibly even AntiImperial nobles!) will have a stronger hold on power here, the reliability of Imperial forces will be more in question. The borders of the Imperium are likely to be broader: for example, with the will of the Emperor more easily thwarted, it's likely that the Solomani would have never left the Imperium. On the other hand, this bigger Imperium will have more fuzzier borders, and more spotty loyalty within the borders (such as they are.)
There are numerous minor strategies, used in ruling a vast number of nobles who are extremely wealthy and powerful: ie, rule worldwide fiefs.
In general, these tactics are perfectly usable in the OTU. They are just 'biggie-sized' and tailored to handle a bunch of dominance-hungry individuals, instead of balancing corporations and system populations.
* Help the People
The Emperor continually spends a ton of money on "bread and circuses." Well, not bread: the Imperium is incapable of building a stable, Imperium-wide socialist network. (Early Sector- and Subsector-wide experiments ended in tears within a century, IMTU).
But it is certainly possible to spend money on entertainment and various festivals. The Emperor sets the pace with the Imperial Games, held once every decade. [I *believe* this is actually canon!]
IMTU, the Emperor also spends a LOT of money on ceebrating the Imperial New Year and the Emperor's Birthday. Various lesser festivals - like Navy Day - also consume a chunk of his money (and, more importantly, his time.) A large wad of cash goes into cultural festivals, generous gifts to impoverished (but highly loyal) Imperial subjects, donations to important interstellar religions, funding conferences for various scientific guilds and organizations, relief for Imperial military veterans (above and beyond the offical Imperial health package), and on and on and ON.
And - vastly more important than the cast outflow - is the amount of time devoured by all these ribbon-cutting ceremonies. Nobles who are busy kissing babies can't spend the time scheming how to replace the local capital ship captains (who are all nobles or knights in their own right) with political allies....
The nobility are under extremely strong social pressure to spend a good chunk of their wealth and time every year on "society". On some worlds, Noble houses have been deposed and exiled for failing to "share the wealth" often enough.
* Serious capital investment
The Imperium encourages her noblity to spend a lot of capital on long-term projects, usually terraforming and tech uplift for their worlds. There are great rewards for this, as the noble who funds these endeavors are allowed to keep the glorious profits (excluding the usual Imperial tax, naturally.) However, money tied up in colonizing the asteroid belt cannot be used to hire "the baddest mercenaries in 20 parsecs."
* Prestige
"Keeping up with House Smith" is a major part of many Noble's lifestyle. Giving the most costly and elegant gifts, having each estate redecorated by the local Michelangelo, having your own 10 sq km. terraformed "Garden" on an asteroid, setting up a private space station at the edge of the local solar system, having your children run "the Grand Imperial Tour" to all the sector capitals (and Sylea, of course!), etc, etc, etc...
* War
Also a major source of Noble prestige is warfare. Due to strong Imperial patronage (IMTU), a lot of this warfare is in the form of bloody 'games': gladiator contests, gunpower-free fights (from sword duels to armies with short swords and catapults), Mechwarrior contests, Zero-G spikedancing, etc.
Despite these substitutes, there are still real wars fought within the Imperium. The Emperor tries to restrict warfare to limit wealth destruction. However, so long as Imperial rule and facilites are not threatened, real restructions on war is left for the subsector Duke to enforce.
* Decadence
In IMTU, Imperial authority unoffically discourages overmuch spending on sensual pleasures: a few high-class, purpose-bred prostitutes should be enough for anyone. However, SOME Nobles (who shall remain nameless, but can rank as high as an Imperial Prince) just don't know when to say 'enough'. Such individuals are encouraged to keep their activities on their own worlds, under wraps so the Imperium as a whole is not shamed by the actions of a few insanely wealthy individuals.
*****************************
Summary:
In a "worldwide fief" environment, the centre of wealth shifts from the megacorps to individual noble houses: military power also undergoes a major shift, from planetary governments and megacorps to noble houses.
(Regarding megacorps: because the Noble shareholders dominate and run the megacorps, instead of non-noble corporate officers, megacoroprations are better understood not as non-governmental businesses, but as alliances of noble-run businesses and interests. They are more fragile, as the megacorp is as fragmented and feudal as the Imperium itself, instead of being a conformist whole under a single corporate identity.)
Now, this has a variety of effects. Imperial stability is weakened to the extent that megacorp culture is broken, replaced by the culture of various noble houses. Imperial AUTHORITY is greatly strengthened, as the restraing forces of sovereign planetary governments no longer exist. The Imperium no longer governs just "the space between the stars", but directly governs the worlds as well.
All armies and all navies are under the rule of Imperial nobles, without exception.
While megacorp culture is largely gone, Vilani, Sylean, and Solomani culture remains unchanged. Networks of allied noble houses will create their own distinct culture, and fill in the vacumm left behind. (The largest and most influencial networks will be Vilani, of course.)
People matter than systems or organizations. Patronage takes on larger-than-life importance, when a single man's will can shift awesome amounts of money and manpower.
There will be greater highs and deeper lows among Imperial worlds. A single Noble genius can gain lasting fame: a single Noble fool can cause lasting devastation. The differing lifespans and cultures of Vilani nobles (200 - 300 years) and Solomani nobles (70 - 120 years) will have huge consequences over time. The values of a Noble house will tend to be imprinted on the worlds they govern.
As the Imperium is more fragmented, there is less likelihood of a widespread rebellion. On the other hand, small-scale rebels can go on and on and on, for centuries. The overall Imperial environment will be more chaotic. However, very few problems will be able to grow past the Subsector level: it is possible that even the (First) Ilelish Rebellion would be basically impossible in this senario.
Because Hostile (and possibly even AntiImperial nobles!) will have a stronger hold on power here, the reliability of Imperial forces will be more in question. The borders of the Imperium are likely to be broader: for example, with the will of the Emperor more easily thwarted, it's likely that the Solomani would have never left the Imperium. On the other hand, this bigger Imperium will have more fuzzier borders, and more spotty loyalty within the borders (such as they are.)