Why are those the ponly two choices? Why not keep it up as a legacy attraction in the park... They CAN make some areas of the island ADA if they wanted to, but not the whole island. Bring back some meaningful food service to Aunt Polly's...which might drive some attendance and get people over to the island to explore again... Most people don't even know what is over there....and it is all pretty great!
Because those are really the only 2 choices that make any financial sense, or utilization of the park sense.
The current version of TSI is underutilized. Disney likely has specific data on this based upon numbers of people taking the rafts per day, but anyone who is at the park can see with there eyes, people are not electing to visit the island, and certainly not in the numbers that other "attractions" are utilized.
So that leaves you with 2 really i guess 3 choices. 1) leave it as is, don't invest time/money in a losing area of the park, and let it just sit there underperforming and costing ROI from lack of utilization in the long run. 2) invest money in turning the island into something people WANT to go see and explore. 3) use the land for something completely new that more people will use and enjoy.
I don't see any logical reason to go with route 1. MK isn't a museum, and the area of land is too big with too much potential to be left as is "for old times sake."
I could see some reasoning behind 2, although i think your going to need major investment in time and money for it to work. The ADA issue is going to be a big one. Your not going to have the same fort/tunnels that you have now. Also i think to truly drive crowds there (i like the food idea, actually I could really see a river side type cafe with seating all along the river in the shade with views looking "in" to the park as being pretty cool....but it would also be a fundamental change from what is there right now) you have to get rid of the raft system and have some form of static ingress/egress to the island (you likely need to do that for the ADA, or completly redesign/replace the rafts to accommodate wheelchairs/scooters, ect.). To be successful you need to have spur of the moment people walking from Tiana and BtRR and seeing lines there and go, hey let me take a quick detour this way. Otherwise unless there is some massive change to the island (and this gets into 3) people don't want to "waste" the time waiting for a raft, getting over to play in a run down fort, and then waiting for a raft to get back.
That leaves us with 3. If people aren't using what is on the island, then you invest money and build something else that people will use. Now I am not going to get into WHAT that should be, at least not here. People can have different opinions on if the choice of what to replace it with is the best one or not. However if your not going to do 1 or 2, all your left with is option 3