Yeah, cool as it would be to have some of these other characters in Smash, I feel like the only ones that actually make sense and would actually have a decent shot, would be either Black Shadow or Samurai Goroh. And Blood Falcon as an echo.
A little under those would be Pico and Dr. Stewart for being part of the original 4, as well as Jody Summer for being probably the most popular female character in the series. I would be happy with ANY of these to be honest!
Personally, I would like to see Princia Ramode. But considering she's an AX-character, maybe not many people even know of her existance, she's not very popular (I never see people talk about her), and she's pretty much Shantae as a racer in a way, who is much more popular.. Princia is never gonna happen. Which is totally fine. She's got basically nothing going for her that would get her included as a fighter. But it would be cool to see her getting a trophy at least.