Lava Stronghold (boss needed to get to it)

Aright, this is my first time posting EVER, and it's not the best idea, but I hope it is. So, after you defeat the Wither you would get a Nether Star, but what if that's not all. It would have a small chance to drop a really rare map that can be used in the Nether. A map that only works in the Nether. It would show you the location of a bunker-ish area that when entered gives you a random OP enchantment (efficiency V, Unbreaking 4). And every time the map drops (just a suggestion) the Wither boss gets harder to beat, as in more health, damage etc... Oh, also If you're really lucky like 1% of the time you get an empty spawner or spawn egg. Any way I just thought of this and I don't really know what will happen but, I hope it goes well.