They should've had an ending where Lamar replaces Franklin, Jimmy Replaces Michael and Wade replaces Trevor.
I'd play this, even though it wouldn't make sense to play as any of these characters.
Wade is my favorite NPC in this game, but he's way too stupid to be a playable character. I can see him trying to reload a gun by trying to cram the bullets into the barrel, then completely forgetting what the mission was and going to get ice cream instead.
As for Jimmy, what would his missions entail? Playing videogames in his room? Seriously, even if Michael was disemboweled right in front of him, Jimmy would be like, "I'll avenge my father's death! ....After I beat Impotent Rage."