Arisme, that would be great if you could look into those issues. I used to play Monkey Island in 5 minutes bursts (bathroom breaks!) and used the boss key pretty much every time I quit (unless I didn't want to save my progress), so would love to see it back if possible.
If you bring it back there's one thing - can you make it so that the boss key save slot is different from the autosave slot? Sometimes after playing for a while I wanted to revert to my boss key save, only to find it had been overwritten by the autosave. Having said that, I don't know if autosave is still in 0.60...