If I Was In Charge of the MCU

So this would be my pitch for FF/Doomsday/Secret Wars setup... I already own some baseball caps, so all I need is a few billion dollars...

Tony Stark in another reality (one we haven't seen yet), failed in saving the universe, stopping Thanos, and any of it. He lived, but almost everyone else died. He lost it, and learning of the TVA, created his own alternate timeline/universe where he had absolute power. This idealized universe is the 1960s version of the FF (because he wants to fix his own childhood trauma still), where he is a godlike ruler that everyone loves and adores. He creates the Fantastic Four, a perfect little family, to be like his 'lil perfect Avengers' that never were. It's the life he would want if he could dream it up. The problem is, that there's an innate corruption to the whole thing. He cannot quite figure out why, but there's a flaw, a malevolent force that wants to destroy it, that becomes Galactus. He gets his buddies the FF (who totally think he's the best) to join him on this big fight against Galactus, and they fail - their whole universe is destroyed, and Galactus is now free to go about devouring other universes as well.

Tony's horribly scarred in the process, feels betrayed by Reed (who realizes what the truth is partway through) and goes full on rage master. He's decided he needs to stop Galactus from eating universes, and he hides out in the Void for a bit to catch a breather and put a plan together. He sees that one universe was able to defeat Thanos, so he decides on a greatest hits, where he will be their 'new iron man' and lead them. Except, he's a deeply flawed one, and the heroes he gathers slowly turn against him. He finally decides to heck with them all - he's going to let Galactus wipe out the multiverse after all, and they can all just pound salt. He assumes the role of Doom at the end of Doomsday, promising to destroy everything.

In Secret Wars, the heroes have to work together to both stop Galactus' rampaging throughout the universe sniffing things out (Doom took out the TVA already, because they kept getting in his way), and has undone the mechanisms that allowed for time travel (that whole quantum zone thing was more trouble than it was worth. Good thing he tricked Galactus into eating it). 

At the end of it all, Doom and the remaining heroes have settled in what remains of Earth 616 (When Galactus ate the void, it destroyed him because it is a place of nothing, so it actually consumed him - or they sort of consumed each other). The multiverse is shut down for good, there is no more TVA, there is no more quantum realm, and we can go back to telling smaller stories set in one universe for a while. I'd even let the celestials take part in all of this (as they rise up and go to various universes to save them, only to die in the attempt against Galactus). I'd want to get that whole dangling plot thread of Celestials out of the way for good.