If the wrench were to be replaced the most sensable/proper step would be to add salvage&repair vehicles in. Which could me made arcady like and repair on the spot in the battlefield or less arcady like and simply act as towing vehicle to tow them back to the main base were a dedicated repair point ("depot") would need to be. Ofcourse that still wouldn't be too realistic (sending out a salvage vehicle straight into the lines of attack enemies? Heh, Repairing the tank in a few minutes rather then after the battle over a couple of days? hehehe), but it's a game afterall.
Salvage & main base repairs would be a waste of time though unless most vehicle spawns would be (more) restricted. Ea, say that only half the stuff re-spawns, the rest needs to be repaired in order to fight an other day. WOuld work nicely in an organized/mature player base, but with 15 year old kiddies running around that jump in a tiger 2, drive it staight into a town and get it shot in the bak and/or bail when a grenade is thrown at it from a windows... ugh.