Who knows how Gennady would even look at 154. he definitely has the power to hurt FLoyd, it's just a matter of will he be able to cut off the ring and actually get to him? If FLoyd exhibits good footwork and uses every square inch of the ring and avoids getting caught up on the ropes at any time in the fight, he could possibly win this fight. But it would have to take the perfect gameplan from Mayweather's part, and good execution of that gameplan on fight night.
First, GGG isn't a high-profile enough name to make this work -- the casuals won't buy it because they don't even know what GGG stands for. Cotto is 100 times more well-known. Second, everyone crowing now that GGG wins by knockout will quickly switch their stances to "weight drained, unfair" if he loses a decision. So there's no upside for Floyd for making the fight -- wouldn't generate the most possible money (Cotto or Khan would be better box office) and there's no credit if he wins. If GGG wants to prove himself at 154, he should drop down and establish himself at that weight.
This is a very good post. The body punching ability could really be the X factor in this fight, but than again what does Gennady's power look like at 154 lbs? It's definitely a question mark, but if he maintains most of it, I could see him hurting FLoyd. I've seen him hurt full sized MW's with his body attack. The problem is, when does Mayweather leave himself susceptible to getting hit to the body? It usually only happens if he's pinned by the ropes/turnbuckle area. So if he keeps the fight in and around the center of the ring, I don't know how effective GGG will be going to the body against a moving target like Mayweather. GGG's not the not the fastest handed of fighters. The flipside is he's never seen a fighter as elusive as Mayweather. he'lll be the naturally quicker man in the ring and he'd have to make sure he stays on his bicycle most of the night and fights moving side to side. ANytime he feels his back on the ropes, he needs to get out of there. His speed could nullify anything Gennady does in there. It would be a very interesting fight at 154, and an extremely dangerous one for a 38 year old Mayweather.
Aside from GGG having a much greater amateur record than floyd, meaning even without his power GGG knows how to box, and he isn't a fast fighter but he knows where to be and when, and has great timing. It would be fair to think Floyd's too fast and slick for GGG to land on him, but then you have to watch GGG throw his arching hook that comes from above and lands on top/forehead of opponents. This punch would ruin Floyd and WOULD land. Very dangerous fight for Floyd, he would have to go 12 rounds without being seriously touched, i don't think this older Floyd could do that.
I don't think GGG has ever fought at 154 and might be seriously drained. At 160, I'd have to lean fairly heavily towards GGG.