You should only be able to repair vehicles from the outside and when they are not moving i.e. if you're in the tank you either have to get out to repair it or another player outside the tank would have to do it and it would have to be stationary, similarly the helis should have to land before they can be repaired

Also attack vehicles should have limited respawns per game. Like maybe the tank would respawn 5 times if destroyed and the helis 3 times max.

Nothing ruins the game as much as multiple almost invincible helis with an engineers onboard dominating the map for the entire game