As far as the idea of running a merc air unit goes, COACC always struck me as an air supplement to CT's LBB4 (Mercenary) that, by the time it went into production, had to be grafted into MT. Given the situations and pay rates for mercenary tickets listed in Book 4, a relatively low tech squadron could turn a profit.
I ran a (very, very) rough calculation on squadron startup & operating costs for TL 6-7 aircraft based on the TO&E listed in COACC. While I'm sure that I overlooked some things, I figure that you could field a squadron for ~MCr 10, and maintain it in the field for ~1 MCr per month, not including munitions expended or fuel costs--I presume that provision for POL & munitions support will be negotiated by the interested parties, otherwise bombs alone can run to 5 MCr per week easily.
The reasons that I went for the lower tech airframes were:
1) Lower maintenance & support costs;
2) Lower infrastructure requirements (unimproved air strips);
3) Better payload/mass and loiter times than high performance airframes;
4) Better chance of local tech support on frontier worlds--where most mercs seem to be employed.
As far as the shipping issues go, a light & lean attack squadron could ship in as little as 1000 dTons, which I figure can't be more than a heavily reinforced mechanized batallion with all of its heavy AFVs and support units....
On the other hand, COACC can serve to flesh out a world/system under seige in MT, too. Enemy fleets show up in-system, and all manner of skilled people may get pressed into service in defense of home & hearth. This can actually serve as an interesting intro/transition into the Rebellion, or springboard for a new campaign. If a party can't decide who to support, having a planet blasted out from under them--especially after a valiant-but-doomed military campaign--will definitely give them someone to oppose!