I dislike your theory, but at the end of the day, I don't really care.
what i WILL stress to everybody here, is that the NEO body is NOT pointless fanservice.
it is a way of showing the repression and, perhaps, DEpression that almost everybody in hometown feels. Mettaton gave up on their/his dreams, asgore's divorced as hell, that one rabbit can't walk her brother
etc, etc
and you can't argue that the people of hometown aren't repressed, because that's where dark worlds and their escapism factors tie in.
They're an escape from the dreary hometown, where sure, everything's fine, but everybody's got problems, nobody's fully open.
The NEO body is a way of showing hometown's discarded dreams
as well as toby literally just wanting to fight mettaton neo
like he said in the newsletter he just wanted a proper neo fight like dude it's not that deep