I say, If I were in charge of a new TMNT product, I'd actually go back to Mirage and dissociate Shredder and Karai, make Karai an older woman and have her appear a few times trying to reign Shredder and the NY Foot in and have them build up an antagonistic relationship, before it explodes into an open conflict with the Turtles in the middle. How she ended up Shredder's daughter has always been bizarre to me.