A gv mission with 20+ m3s would be difficult to stop. I would suggest 2 troops to destroy 1 building or something of that order.
Three spits could take 2/3s of that convoy out with little effort...M3's are firing 303's or 50's right? Besides, I haven't seen a 20+ volunteer group of 20 of anything on a regular basis. They would have to get by base ack, field ack, town ack, any GV's that are up and rolling, fighters, heavy fighters...one 1000 pounder might be able to kill 20 if they are clustered....or moving together. One answer might be that the troops force is cut in half if the guy that ran them gets killed...so the M3 or C47 would have to stay alive....just spitballin here.
Damage is up to HiTech...but it would compliment the ground. Hey, I know this is an air game, for the most part but we have um, lets use um fairly. You guys can come up with answers too...you've been in the game for a while. Find the advantages like you have and present a way to limit it so it can't be used to overwhelm...troop speed, limited weapons options, limited ability to damage, base flashes differently when troops are in the DAR ring...hell I don't know but it could be a good addition without a ton of argument and we already have the troops.