A possible solution to tanks sitting in HQs

We all know the issue: a player decides to grab a tank and just sit in HQ and snipe from there. Now, I think people should get to play the way they want, but in this case, it really denies the whole team an important resource. It's worst when the tank player isn't even sniping but sits on the mini bird spawn out of spite... (Yes, I actually saw that happen, and not just once). 

I was thus wondering if we could have a simple system to avoid these situations. I'm proposing a simple timer, say 2 minutes, after which, if the tank hasn't left HQ, it becomes "up for grabs": anyone spawning in it of running to it and entering gets the driver seat, the previous driver gets moved to another seat. If the team is alright with that tank sitting in HQ, well, that player can tank-snipe to their heart's content. But if not, at least there is SOMETHING the team can do.