To be fair, I could easily see Crimson Viper being a character in the Marvel Universe:
A single mother (there is a surprising number of single parent super-heroes in the Marvel U, including the Julia Carpenter version of Spider-Woman and the Scott Lang version of Ant-Man) moonlighting as a mercenary, who uses martial arts and a special suit loaded with gadgets that simulate super-powers? It practically writes itself!
Yeah, stick her with the Heroes for Hire, or with those two ladies who sometimes team up with Luke and Cage (I think Misty Knight was the name of one of them, but I forget the other one).
Or go the same route as her ending in MvC3 and have her recruited into S.H.I.E.L.D. by Nick Fury.