I would also love to know how to do this. Quite mind-boggling that this isn’t addressed anywhere. I see tons of videos that show how to add other stuff to GASP, but to make the default walk animations look less like a cartoony male seems to be impossible.
Having said that, GASP is still an evolving beta, and the latest update shows that the team realize it’s not exactly artist friendly or expandable. The addition of experimental state machines to GASP may make it easier for us to override these things in the future.