Battling 'on location' is something that I rather like the idea of. Inside Battersea Power station for instance, or inside an emptied Robochallenge workshop; something that wasn't designed as an arena specifically but has all the space, strength and a certain level of randomness to it that would create some interesting fighting.

I am also of a mindset to ditch the House Robots and come up with an arena that gives a more balanced or even changing set of challenges. The very first RW arena in 1994 had sliding barriers at either end, imagine that now so you can to robots over them but you have to time your flip and be able to get your opponent in the right position at the right time to do it. I like the idea of the Pins from BB, so all those spinners have something hard and unmoving to ricochet off.

Cluster-Bot rules need changing really, so you have to kill 67% of the robot by weight to win. That way double or triple clusters will have a good chance, even if they might end up like that Warrior Clan minibot :-P

I also think, just like in BB, competitors should be allowed flame throwers. They may not do much 90% of the time, but they look good and can present problems under the right conditions.

Finally... I think that Battlebots and, for the sake of simplicity, Robotwars aught to allow robots to enter each others events, none of this being locked to one event or another. Having the Trophy come under threat from 'foreigners' and having 4 on 4 US vs UK annihilators... insanity would ensue! And being able to see contrasting design styles and philosophies play against each other would be a really interesting dynamic (Notice how all the US bots have one build style and the Euro bots have another)