Im currently in a position where my robot would stand no chance in the current Featherweight class, but it also wouldnt fit into the ideas for the lower class suggested above (eg. Im way over that budget and will be using some Titanium).

Im just going to suggest a spinner and non-spinner class. Those that can afford Hardox and Titanium or feel they want to go into the spinners league they can. Those that do not have the funds, armour or courage to take on the spinners could go into the non-spinners allowed league. But then that wouldnt stop anyone having DeWalt powered rammers and Full Pressure flippers. So maybe the way to go is to have a limit to each weapon type...

Low Pressure Flippers - Lower League
High Pressure Flippers - Higher League
Rammers (Under ???hp) - Lower League
Rammers (Over ???hp) - Higher League
Spinners (Over ???rpm) - Higher League
Spinners (Under ???rpm) - Lower League

You get the picture.