I guess it depends a bit on what you put into the term genderswapped. If it's writing the entire thing with the characters gender changed from the beginning then I guess I would call it femslash too, but if the characters changed gender in the fic for some kind of magical reason I would be more hesitant. But then, it could go both ways depending on the author.

I try to use the word guyslash just to mark that it's not so much derived as two different things. But I think I'm one of the few that do. And femmeslash doesn't work because to me, femme is someone who plays in the femme/butch thing, and fem would imply female. But this is just my own opinion.

Thanks for reading and commenting :)