Should Ghost Spider (AKA Spider-Gwen) be part of the regular Marvel Universe?
Yes, there is an ongoing similar thread about Miles Morales, but Gwen's is quite a different case, and should be discussed on its own.
Miles have an advantage that made the move a bit easier: Ganke, Jefferson, Rio, Bombshell, etc; are all brand-new characters, as well as Miles himself, and can be moved with no problem because they do not replace or overstep anyone (well, Bombshell replaced the original one, but nobody even remembered she existed to begin with). Some of Ultimate Parker's cast (Aunt May, Mary Jane, Gwen Stacy, Jessica Drew, etc) were still around with Miles, but did not made the jump. Unsurprisingly, those who had original versions in 616.
And that's the big problem with Gwen's cast. George Stacy, Uncle Ben, Aunt May, Harry Osbourne, Mary Jane, Peggy Carter... they are all available, in some form or another (either alive, or dead but still remembered), in 616. Moving that cast to 616 would cause plethora of problems, which can't be solved easily. It's as if we tried to transplant Ultimate Peter Parker to 616. The only way they can make it work is by leaving her full cast behind, so that she is completely alone... and that would be an absolute disservice to the character.
