As fun as it is having the robots we currently have, the multiplayer avatar customization gave me a little idea. Why not just have it so you can make your own custom robots instead of relying on suggestions? Want a mint jetpack bot that summons robots whilst speeding around? Done and done. What about a Green Fleet Captain that can block every arrow you shoot? Consider it complete. Looking for a basic pink mark 1 sword robot that's completely defenseless? Right this way! The possibilities, could be nigh-endless! Simply take any of the existing robot models, give them upgrades, give them a preferred color, size and speed and then top it off with a name, and boom! You now have a new robot to play around with. Of course these bots could even be included in challenges and endless mode levels, automatically being given a calculated difficulty score (how endless mode determines what robot arrangements are in what tier) based on their model, upgrades and such, and can then be used to your heart's content, or to the content of others if you decide to share it publicly. Easy, Squeeze, lemon human life!
Here's a little conceptual image I made just to sort of, give an example of what I mean. Of course this could easily be elaborated on or what not, and hey! That's just more replay value in the end, so nothing wrong with that. And with that, this concludes the base concept of my idea, any suggestions I'm all ears to hear.