I remember a few years back I wrote something similar. Basically, revamping Venus entirely not just ability-wise, but animal-based too. Needless to say, it would just result in an original character.
I think Venus gets a bad wrap, as does most of Next Mutation, for being a product of its time. The effects and setup definitely don't hold up, but a lot of the concepts do. (I'd
love to see Bonesteel again.) For her to succeed, I feel you need to address the following:
- Her origin, and as a result, her relation to the Turtles. (sibling, friend, love-interest?)
- If utilizing a different style of martial arts, address it. Make her unique (not stupidly calling her a "shinobi").
- Make her stand out from the other Turtles.
- Arguably the biggest thing, if Saban owns the show rights instead of Viacom, you need to buy it to use her or the other characters. Then again, you can always loosely use them. (I don't know the copyright battle off my head; feel free to correct me.)
I don't know if her being a main character will work without criticism, but a recurring character definitely. Venus should be used at some point, or any Next Mutation character deserves a revamp.