There are fields I have played at where the tanks can not be eliminated even with a rocket, they are absolutely invincible. It just adds to the fun, because you hear people down the road yelling and you can't quite make it out, then it gets louder and closer until you realize what they are yelling. They are all yelling "TANK" over and over in unison!
By the end of the day every time you hear a group of players yelling together you start looking around for the biggest freaking log you can find because you want to have a huge bunker to hide behind when the tank gets close.
I remember getting in a spot I thought was safe to find out the tank would pass right by and have a good angle on me. I pressed myself into these bushes as hard as I could, they were thorn bushes and I was bleading all over by the time the tank moved on from the thorns sticking into me. But the hundreds of paintballs flying just inches from my head made me care less about the thorns as the seconds ticked on and on and on.
I do think a button on top of the tank is a good idea though, but I also see value in making sure only a rocket can take it out. In real life tanks can't be taken out with buttons, and it is not very realistic to think you will open a hatch and drop a grenade down.
I am not sure how the tank rules went, but what would help is to require the tank to always keep moving forward - not let it stop and dominate an area for more than 10 seconds or something.
