I'm not an architect or engineer so feel like I'm pretty ill-qualified to opine but I've always heard that type of restoration work is prohibitively expensive.
If OT were to be turned into a sort of 'smaller second ground', then I'd expect it would be a full knockdown & rebuild, not a restoration of any of OT's existing structure.
Edit: Also, why is 90/95k the maximum? Has there been any good analysis published on that?
The easiest thing to do is keep the South Stand and knock everything else over time and replace with smaller stands.
The South Stand has all the things required keeping.
As regards 90k/95k that seems to be the natural limit for football stadiums for some reason.
American football stadiums go over 100,000 though.
The guy on the Stretford paddock was saying we'd be the only 5 figure attendance in the PL and Europe also, so it's kind of a status thing. Also he wants to sell cheap tickets to young people to improve atmosphere.
I'm actually not too fussy anyway.
As an Irish person Old Trafford is still magnificent to me but I've used to shitty Irish stadiums and haven't been to that many others.
I did notice last time I was over that the concourse in the south Stand was very old fashioned and tight.
I'm 5'10 though and didn't find the seating cramped.