"Teleport-only" humvees and 4-5 humvees always empty on the base is a signal that its useless
If that humvee will become with mounted autocannon - you will see everybody will use it.
Of course if autocannon can rotate to 360 - it will be fast APC that is OP.
I suggest rotate autocannon backwards by default and allow rotate to +/- 45/60 degrees. Enough hard to play, requires much teamplay to operate, and so... you get APC cannon without APC.