Suggestion name: Battle Bots
Think of robot wars or whatever that show is. People build these deadly robots and then make them fight until one dies and is crown the winner.
You could make it like the clay solider mod.
http://www.minecraftforum.net/…soldier-mod-v2-new-stuff/
You don't actually control the bots, you just place them and equip them with weapons/armor etc to be stronger.