Why Floyd should fight the winner of Pacquaio-Cotto over Shane Mosley ?

I actually agree with you on this. Floyd Mayweather will be out of his mind if he picks Mosley because it is almost a no win situation. If he beats Mosley, people will say he is old. But again if Pacquiao beats Cotto, and Pac face Mayweather and Mayweather wins, then people will say Pac is too small. I got to tell you, Mayweather should pray that Cotto beats Pacquiao, because beating Cotto in my opinion provide Mayweather more legacy, as he beat the man considred by many as the true welterweight champion, and Cotto is bigger, stronger, and younger than Mayweather.