It just wont work, the key word here is depth and I'll explain precisely the issue in the next paragraph. if he has to fight his way thru the ladder like a boxer chances are astronomically high that he faceplants once he gets up to any sort of decent competition.
These (smaller dude) weight classes that he'd be in are super-loaded --- There's a reason why sometimes Boxers have to wait tiltheir 30's (and the top competition is STILL ducking them) to get title shots sometimes and conversely in the UFC you've got champions with less than 10 wins (or Brock Lesnar just getting title shots and reduced drug testing sanctions whenever he wants LOL) that reason is the depth of talent at these weight classes.. At some point the water is gonna get way too hot to handle and trust me it's not gonna be some big money fight --- Some dude waiting for a big money fight will make an example of him something serious.
I mean this with no racism at all attached but just to make an example - there's like(several)Japanese dudes and south americans and africans and fighters all over the world that would be licking their chops to get MacGreggor in the ring...
If somehow he made it to the level of a real title contender, that'swhen the party would end.
There's no way he could ever work his way up to fighting floyd legit, there's so many dudes more deserving he'd have to beat.. Floyd is like beyond final boss status, he'slike the dude who won the game and still hangs around to remind everyone who's the best.