Again, it's all stuff you can work around. The guy doesn't have to "attach" C4, he can just tap the hull of the car with his hand; tap the vehicle "out", essentially.
The laser idea is easy to work, and you can set up a simple sensor that would trigger a light inside the tank to alert the driver that he's out, or something like an alarm.
I know that in so called "big games" in the states (specifically paintball) vehicles exist and are used. I've heard of dunes buggies, sedans, surplus light tanks and even helicopters (if you can believe that!). That means that there's not only precedent for this, but that guides on how to work this must exist somewhere...