What fights do the general sports fans want to see that will help elevate boxing again? What fights will attract the most media attention? What fights will ultimately make the most money? There are only a very few.
I will go with the obvious and say Pac/Mayweather. These are the two fighters that the general sports fans will pay to watch to some extent even if they aren't fighting each other. When/if they do fight it will be huge.
A Klit/Valuev would have stirred interest up to the Holyfield fight. That was a lost opportunity. Other than Pac/May, I don't really see anything. Maybe a Klit/Klit.
There's only one answer to your 3 questions. The Pac/FMJ fight. It will garner the most money, most media attention, and what the vast majority of boxing fans want to see.
I'm reaching here, but there really aren't a whole lot. Just PBF-Pac, obviously. But if DLH came out of retirement to fight Pavlik at middleweight that could probably do okay. DLH is obviously a seller and Pavlik appeals to a lot of white Americans.