Here's what I've been thinking - how about separating the "resupply" funtion from the "repair" function?
1) GVs will not be repaired with crates of supplies. In order to repair a GV, a friendly M3 must come within 10 yards of the damaged vehicle, and activate "repair function".
2) The "repairs" a M3 initiates, will not be instant. Each damaged component on the damaged vehicle will take different amount of time to repair.
* tank turret = 2 minutes to repair
* AA vehicle main gun = 1 minute to repair
* engine = 2 minutes to repair
* tracks = 1 minute to repair
So, if a tank has turret, engine, and left track damage, it will take total 5 minutes to repair. A friendly M3 must come within 10 yards of the damaged GV, initiate the "repair" function and wait for 5 minutes.
3) The "supplies" a M3 carries, will only resupply the ammunition on the GVs.
.....
IMO, this change should bring lot of small but benevolent changes to the GV warfare.
If M3s have a separate repair function, that will get rid of;
1) the instant-GV repair problem
GVs being instantly repaired with 'resupply' crates.
2) the "spray the field with supplies" prolem
People spawning M3s in defense positions, and spraying the entire area with hundreds of crates of supplies for use
3) the "selfless volunteer" problem
People hate to do supply/repair runs.
An organized GV assault is very effective and desirable in terms of gameplay - however people seldom do supply runs becuase it has no rewards, and remains a pure voluntary action.
However, if a M3 can repair GVs, and receive hefty perks for that action - then it might become a good part of the gameplay in the future.