Kk that's fine. Again, as long as the criteria of it remaining defended by a sizable group is met, it shouldn't be an issue. I just wouldn't be able to get past the notion that something as rare as a functional tank is out there with one or two people and bigger groups haven't taken it.
There is also the question of, if a stationary settlement in the Wastelands DOES have a tank, what's their purpose for deploying it? It'd be better off kept safe and hush-hush, saved until they really need it.
Sorry for all these edits, but I need to stop double-posting. x.x
I guess I should say that if you wanted to, you COULD roll a char or two with a tank, but it would be unlikely that the characters would have the tank for terribly long. Maybe someone or some people escaped from a settlement with a tank as it was being destroyed? They lived by using the tank to get out. But it'd just be a matter of time before it was taken.