Well FFD allows 6 fighters to directly support a formation. But as mentioned, they should probably target prioritize based on unit base type. Largest vehicles get bombed first, and it goes down all the way to light vehicles as appropriate targets run out, finally bombing infantry when there's nothing else left. Otherwise you can keep the randomness based on tonnage.
There is also the problem that as it currently stands, using any moderate amount of CAS fighters is an exercise in frustration, as there is no way to quickly assign CAS to support formations and you must do it one-by-one. I tried using 42 once, I will never bother using CAS again after that.