A system to make a signature power would not be hard to make. you'd choose a visual FX and a mechanical FX, and there would be some restrictions to prevent taking everything to be OP and nothing else, but you'd still get like 3-4 aspects to combine for a signature power.
Maybe even allow people to have an emblem in the power FX, seperate from their SG emblem, a personal emblem. so my character Astera could have the Stellar Punch, a super heavy aoe exploding punch which shows a big yellow glowing star of the same kind as her chest emblem.