Ok yeah, I admit that having abandoned vehicles in the field and no tanker kits around would be somewhat of a bummer.
What I mean by stick vs carrot is that you could either simply force people to use the kit for tanks (stick) or grant some sort of bonus to tanker kits making them operate tanks better (carrot). Doubling the reload time for non-tankers would be an incentive to use the tank kit (example) but it still doesn't address a lot of what forcing the tanker kit was trying to address.
While I don't like slow gameplay in its own right, the game has to play at the same pace as the tactical elements within it. You can't just make strong tanks infinitely strong via some unreal mechanism.
I like how the tanker kit currently is. It has the two most important things a tanker needs, the wrench and the binoculars. Then he's got the pistol as a backup weapon. The wrench and binoculars is enough for me to chose the tanker kit am I planning on tanking. However, it would be nice seeing the American tanker kit get a carbine.