Just put 8 robots in, 2 from each team, and when both robots from each team are out the team are out.
At the end of the fight award the teams 1st - 4th place on whos left running. That's like an Annihilator without the messing about of stopping a fight half way through ! :-)

That's what Andy Kane's issue at the O2 was because he couldn't understand as a show annihilators don't work, the fight has to last the full distance or it could be over in 5 seconds and that's no good.