Losing Muppet*Vision would be, all by itself, a major creative loss for the park, because it's a great attraction.
And even beyond that, replacing an easily-accessible attraction with a ride that has a higher barrier to entry would be a major, major mistake for this park. Hollywood Studios needs more things for guests to do --
quality things -- that do not require waiting for an hour-plus or paying an upcharge to skip the line.
Unfortunately, I also believe MV's plot is the better choice than AC. The offices need some more time to be moved around, that area deserves a more significant expansion, and needs to finally complete the loop over by the McQueen soundstage. None of that would be offered with Monstropolis, which over by Muppet-Vision would hopefully match (MV, Rat Pizza -> Laugh Floor, Harryhausens) and expand on it (Door Coaster).
We don't know for sure that Monstropolis, were it to go into the Animation area, would prevent additional expansion back there (there is a lot of room if all/most of the buildings go away) or the creation of the connection over to Sunset.
So I remain generally against holding onto the Animation plot for something bigger/better, because:
1. We don't know when -- or even if -- that expansion would ever happen.
2. I don't want Zootopia, which seems to be the favorite rumor at this point.
Putting Monstropolis there does much more good for the park, in my view. It would expand the park NOW, would allow Muppet*Vision to continue to fill a niche that the park needs, and would keep open the possibility of additional expansion adjacent the Monsters in the future.