oh man
I just spent over 4 hours playing that game...
a few quick ideas:
1. sound toggle button (I'm not a big fan of the music you chose, so I just turned it off!)
2. More stuff to buy (the idea's you listed in the reponse sounded great, but also, you might want to think about making upgrades availible for all elements of the bots, ie propulsion, targeting, range, and CPU IQ so that maybe they wouldn't kill themselves on the walls!)
3. some "gimmick" arenas (arena's where there would be some sort of traps set, or extra wall sections put in or something)
4. NPC's. Has anyone played Death car rally? one of the coolest thing about that game was when you prefomed an action (ie killing all of your oppnents) and afterwards an NPC (in this case death himself) would ethier reward or punish you.
5. colour scheme just let me pic the colour of the light on my bot, please! i would like the colour green if it isn't too much trouble. Still, that game was great fun! I can't wait for another version!!!