I've thought about this and I think the best option is build a brand new stadium at OT with a capacity of 80,000+.
I'd keep the old OT. It has too much history to demolish.
Keep the South Stand as I think it's the most historic and parts of it go back to 1910.
Then reduce the capacity of the other stands to whatevers needed. Maybe 20,000
The old OT will be used for women's, youths, reserves etc.
Women's football has growth potential and I think playing in such an iconic stadium would give it a boost and attract players.
It's also cool for Youth prospects.
Then we're retaining all the soul and history whilst getting a brand new stadium at same time. Best of both worlds.
Imagine we're trying to attract talent for the youth teams and we can say "you get to play on same pitch as Best, Ronaldo, Rooney" etc.
it's completely unique