I went there for the first time around two weeks ago and it is quite a place. I kind of got mixed feelings over blowing it all up.
Maybe they figure out some kind of incentivized model so that the stadium is renovated properly and clubs benefit from it financially as well. Investments to the surrounding area etc?
I've been to hundreds of stadiums.
Honestly, none in Europe has a greater feeling than the Meazza.
The closest is the Bernabeu, but reserving further judgment until it's done being renovated.
And this doesn't stem from some sort of bias, recently a lot of people I know went there for a game for the first time and they support random PL teams or just random teams in general. They all agree that it's special.
It just has this effect when you stare it from afar as if it's the hottest model in the world and once you get inside it's just a remarkable feeling of losing your breath momentarily only to realize that you're indeed inside such a sporting venue specimen.
It's hard to fall in love with buildings, even as someone who professionally kinda creates them from scratch, but what you get there is unmatched.
As to how to fix it. Well, scrap the 3rd tier and add corporate shit there, improve the existing areas, maybe add a 3rd tier on one end, fix the plumbing (seriously) and the basic infrastructure, replace the seats and you have the best stadium in the world.