In BT lore almost every merc corps was heavily dependant on salvage to maintain their fighting strength. Even new mechs for the corps were almost always just salvaged machines.
From your laid out plans I got that you aren't able or willing to introduce more than the current CBill bonus for salvage.
How about a soft salvage system that distinguishes mercs from house units, which will get certain discounts for house specific mechs?
My suggestion would be to introduce a system of discount per mech kill. For every kill a merc does, he gets an 0,5 - 1% (i.e.) discount on that mech variant, accumulating to up to 10 - 20% discount on the black market price. Discount per kill depends on the status of the wreck, of course, highest percentage would be only given for a headshot kill, as it works right now with the salvage CBills.
Lore background for this could be that if you have already gathered parts of that mech, you can buy cheaper chassis from the black market, which are in a worse shape than you'd need normally.
This system would also heavily spur competition within the units and lead to a more "merc-like" atmosphere.
As a bonus this system uses only stats you're already tracking anyway and chimes into your planned discount system for house units.
As a consequence of this you can make your planned planetary assets for merc corps more expensive and rare, which would also better fit BT lore.
Edited by Shredhead, 10 March 2014 - 08:48 AM.