The Olympic stadium can be renovated, but it will never be meaningful enough to get to MLB standards long term.
The biggest problem with the stadium is how large it is, and you can't really adjust its structure because of the idiotic architect who insisted on the "Fingers" structure of the stadium which he was unwilling to bend from.
That fingers structure pushes all the seats back is the problem. In 2014, I went to the first preseason game back in Montreal that drew about 50K. It was a hot ticket, I decided to go to late and I had about the 40,000th best seat in the place. When you are in the upper deck down the 3rd base line you are well over 100 feet away from the field.
I would compare the experience to having the 30,000th best seat at the Carrier Dome. The sight lines are not friendly. But you can't do much about it.
The seating is decent enough right behind the plate (upper and lower) and in the lower section between first base and third base. But it gets bad very quickly after that. That being said you put 40,000 fans in the Owe and its louder then most stadiums and certainly the Skydome. Montreal fans across anything are loud -- be it hockey, baseball (heck some wrestling fans may remember the ovations they gave to Hogan in the early 2000's).
So now I will reminisce
The loudest sporting event I ever went to was mid September 1993, a Friday night against the Phillies when Montreal was pressing for the playoffs. When Curtis Pride, a deaf player making his debut in the Owe, hit a pinch hit double to tie the game the ovation for several minutes was unreal. The place felt like it was shaking... actually I am sure it was shaking for a few reasons.
The Expos would also get huge crowds for Opening night as their small remaining fanbase would see this as an annual gathering. The 2000 Home Opener also had one of the loudest moments I had ever experienced. Tim Raines was making his comeback with the Expos and the Expos fans were loud in his first at bat. Glendon Rusch was pitching for the Mets and was clearly flustered by the noise. The fans could sense this and after the count started at 1-0, the crowd got louder and louder. It was the largest continued ovation ever for a 4 pitch walk.
I was lucky enough to go to the 1993 Curtis Pride Game, the 1994 Cliff Floyd Homer against Maddux game, and the 2000 Tim Raines Walk. Unfortunately Expos fans never got a playoff stage after 1981, and don't have a Joe Carter moment. And those moments are more of our own, and not huge in MLB History. But for us, especially the ones that stuck to the end they are very special.