Fascinating thread...
First read through kept reminding me of Avalon Hill's old Merchant of Venus game. Like Republic of Rome from the same company, the players competed against each other and the game. (IIRC, there was an alien race which appeared somewhat randomly as raiders.)
Everyone is a merchant in MoV moving goods and trying to avoid the raiders/pirates. That's fun, but it doesn't work for the varied styles/types of play you're looking for.
Second read through reminded me of Stars Without Number's faction rules. Those rules are meant to produce a continually running/updating background for the referee's campaign. The referee can then insert his players into any event the system produces and their actions can then influence the outcome.
Factions in SWN can be pretty much anything; planetary governments, merchant houses, cults of various kinds, intelligence agencies, criminal organizations, free traders, anything. They're rated for things like size, wealth, cunning, and so forth. They can buy, earn, use, move, attack with, defend with, and lose different kinds of assets. Certain types of assets are only available to certain kinds of factions. Factions can also be assigned different kinds of goals.
Players as factions might be an interesting mechanism.
Riffing off your riffing here... Tukera/Marquis Aramis is a faction controlled by the game/system. It's the competitor all the players need to worry about. The players themselves are one of several factions within the subsector/game map. One could be Oberlindes trying to break into the market, one a government flexing it's muscles among it's neighbors, one a free trader crew just scraping by, one the local Ine Givar, one a noble house trying to unseat the Marquis, and so forth.
Each player has different goals, different starting strengths, different starting asset, etc. The players will interact with each other indirectly and directly. "Winning" will depend on how they well they meet, fail to meet, or exceed their goals.
