don't think Margarito could make 147 TBH. If he did i think even at this stage of his career he'd have to much for Khan.
Look if and its a big if Margarito could get back down to 147 I think it would be a desent match up with Khan. Could he deal with the kind of pressure Tony brings? Making him boil back down to welterweight possibly leaving him dead at the weight might sound good to Roach(similar to when Manny fought Oscar).