I think suggesting that only Iwata can keep Nintendo from getting worse is a lame cop out. No one who wants him gone is suggesting to replace him with an idiot who will run Nintendo into the ground. Obviously I want him replaced with someone good.
You might not want to hear this, but he's pretty much the only good one there is. No, seriously. Take a look at all the kneejerk dumbshit decisions that the rest of the game industry makes. Every last one of them is either trying to get "CoD-like sales", or is chasing the Mobile unicorn. How many of these people running these game companies actually know anything about videogames? Hell, how many of them have even played a videogame.
I see no reason to have any faith whatsoever that a potential replacement would be better than any other gaming CEO.
But none of this matters, anyway. He's not getting fired, he's not stepping down. The #FireIwata dream is dead.