Ive been thinking about making a cluster bot too but where is it covered under the rules? Is it an unwritten rule that the robot must drive in as one? What rules are used to decide the winner of a fight? Is a clusterbot out if one robots dead or is it 50% by weight?
Personally I think the robots should be able to drive in separately and there shouldnt be explicit rules about how much of a cluster bot needs immobilising. If a robot can continue with only half its drive working and a dead weapon, then a clusterbot should be able to continue with one of the robots dead.