Disney's takeaway from a "violent revolt of rampaging gamers" will be that this IP is tremendously valuable, which is probably the opposite impression you should be cultivating if you want to buy it from them at a low enough price to make third-party development itself practical.

If he wanted to put the effort and time to make this game, why would it have to use the Monkey Island IP?

I think that any new game with same quality, the humor and mechanics, but in a different setting (or heck, just a different name!) would still be loved.

Using existing IP is a lot safer, and will generate more sales, even if otherwise the games are the same. There are a lot of people who played Monkey island in their youth and are nostalgic for it, but who don't follow the latest game news and wouldn't auto buy a game without the IP. Yes it could be successful, but that the Monkey Island name it would be more so.

See for example the success of every new Civ game compared to the success of other strategy games.