Self-unhook needs more conditions
While I do not mind the removal of self unhooks too much, there are a couple scenarios where I think it should be possible. Even if they're not guaranteed, just giving survivors a chance to make a comeback is what makes the game exciting, when all hope seems lost.
Most importantly I think you should be able to attempt self unhook after the gates have been powered. This is where killers tend to camp the most. Some killers like Bubba, Billy and other instadown killers can guarantee you can't be saved. Ranged killers can usually guarantee no one makes it out of the basement. So going for the kobe is your only chance to get unhooked. Other times you want to tell your teammates, that you don't want to be saved, by trying to hurry the sacrifice process. At this point, you're so far into the game that it doesn't matter if you go next on purpose, so I really think self unhook should be unlocked there.
Also, in my opinion your should be able to attempt self unhook, if you've been left on hook and are about to enter stage 2. Just one or two attempts would be nice, at least maybe you have a chance to kobe, when your teammates decide not to save you, or if the killer has been patrolling your hook for long, but not filled the anti camp meter in time.