I seem to remember reading that the motor needed is a "340" but when i went looking for those nothing looked promising. I just couldn't be arsed to learn enough about rc to understand what was on offer etc, but maybe that means something to you? Unfortunately there isn't enough room in the width of a Scorpion to fit fatter wiring, although I am thinking about doubling up the 20AWG stock wire, although TBH since i added a Pico AB MOSFET and 7.4V LiPo it is doing pretty well.
But... the next round of upgrades will involve a set of SHS gears, Kanzen bearings, a magnesium alloy piston, and a 130% spring - i'm looking for higher FPS to make it useful as a primary weapon, not just a sniper back up. The problem is that these things suffer from terrible trigger response as stock and although that is now sorted, I fear that the new spring will bring that problem back. I have ordered an 11.1V LiPo... do you think that will fry the stock motor? Bear in mind that even if I were to double up the wiring, the construction of the thing requires the current to flow across some pretty dodgy brass connectors, kind of like spade connectors, otherwise I'd have to radically rethink the way the grip/battery compartment is attached to the lower receiver, so even with a MOSFET it's not the same thing as wiring a hot LiPo directly to the motor...