I think we should think about it for another 75 years. No need for rash decisions.
Why not let Mel Cooper and company take it over? With a little work a huge amount of other people's money, could have a first class development in operation for as long as three months.
As to 99 year lease: I had that thought, but the lease would be with the owner. She is likely to die soon (math-wise: husband died 30-50 years ago so she has to be 50-100 years old). If she isn't going to sell it she isn't going to transfer it to a third-party corporation that has a life of its own. So when she kicks it, I could see the property going up for sale and leaseholders being shown the door. With that said, if a lease could come with two clauses:
1) a first-right-of-refusal for any sale of the property then the lease concept could fly. When she kicks it, some bitter nephew inherits it. He honors the lease or sells the property and the lessors would have the chance to buy it.
2) cancellation comes with payback. If the owner tosses the lessors, the owner would have to give them a pro-rated payout of the improvement costs (e.g. if the roof and paint has a lifespan of 30 years, tosses them in 10 means that the owner is on the hook for 2/3 of the roof and paint costs plus interest).