I wonder if we could do such things using something less magical than plugin hooks. It's definitely first thought, but it's always a bit less intuitive when you start having lots of them.

It looks like very natural use case of menu system.

There's the question of additional pages for existing page handlers. You could use routing system for it, though it's not very elegant solution. I usually add manually a plugin hook inside of page handler itself that allows to tap between existing cases and default one (or failure). That's the good case for new routing system..