Maybe instead of one shot one kill... the power ups bolt on a weapon or special article to your tank, and if you get hit, one of them gets blown off. If you have no weapons attached, the tank gets blown up. Perhaps these power ups could actually come from either blown up tanks or the weapons being blown off them.
Ideas for power ups:
Longer shots
Faster missiles
Higher firing rate
3 missles
Back firing missiles
Homing missile
Exploding missile (even if it doesn't hit anything, blows up after certain distance with blast radius)
Mines
Go Faster
Turn Faster
Invisibility (would be difficult in split screen I know)
Shield
Teleport
Tractor beam (pulls special items to you)
Minitanks (small AI controlled tank that you can let loose to hunt down opponents for you)
I also think making the scenery destructible would be cool.
Ideas for power ups:
Longer shots
Faster missiles
Higher firing rate
3 missles
Back firing missiles
Homing missile
Exploding missile (even if it doesn't hit anything, blows up after certain distance with blast radius)
Mines
Go Faster
Turn Faster
Invisibility (would be difficult in split screen I know)
Shield
Teleport
Tractor beam (pulls special items to you)
Minitanks (small AI controlled tank that you can let loose to hunt down opponents for you)
I also think making the scenery destructible would be cool.