Would Matthew Hatton beating Floyd Mayweather be a bigger upset than Tyson-Douglas?

Yes.

Tyson and Douglas were heavyweights, people get unexpectedly KO'ed at that weight quite often. Douglas could punch too, so although it was extremely unlikely, it was possible.

This looks like an impossible situation for Hatton.

 

Hatton all day & all night as he's bigger than pacman & void has just legged it from the little guy who less than 2 years ago was a super/featherweight so i can't see how that gutless cherry picking turd void mayweather can possibly beat a genuine WW simple as, the facts speak for themselves