Okay I'm thinking of doing a Super Robot Wars styled RP

I'm rather new At the GM thing so I'd like to get help working out a system for power levels and whatnot, or just doing plain 

I'm thinking up a storyline 

You will be permitted one OC character in addition to a canon character be they hero or villain for now

I'm thinking later on you can get an additional two charicters if we last long enough

No EOS mechs until second half
No godmodding
You are allowed to Choose from a multitude of series. You are free to choose whatever for your own Char of course so as long as they pilot a mecha