Just a few ideas here,that i reckon could help out the gameplay a bit.
1)Construction vehicles
--have a craft that can build defences( bulldozer ?) the ability to put up walls/berms or other obstacles to slow down the enemy,obviously a balance required here,but if anyone designed a base where you could just hurtle in and out or race around and shoot the defenders would be shot at dawn.
2) Combat Engineer Tractor
either a purpose built vehicle or a cert buyable mod for a tank that allows you to plough/detonate through the mines that litter all over the area,and the ability to destroy barriers ( as above )
3) Battlefield hospital
a deployable vehicle that can be used as a field hospital,a certain " bubble " or force field around it that slowly heals all inside but prevents you shooting out----and here the good bit---enemies outside the bubble can shoot in at the patients but get a huge grief penalty for doing so......
6) hover bike etc etc
The vs love their hover vehicles,so give them a Wraith like hover bike,no weapons,no invisable just good old fashioned speed and ability to cross water..
For The Tr, maybe a basilisk with faster firing gatlings with even larger ammo hoppers..
For The NC,possibly have a basilisk fitted with a big powerful and slow firing 20mm autogun-good power against hard and soft but slow rate of fire..
7) FLAMETHROWERS---i say again FLAMETHROWERS
no self respecting game can exist without a big,friendly,Bar-b-q on legs
thats it really, but this could be great stuff for a future update