I'm sorry but there are several flaws with that design, and if you would take the 5 seconds to look around, you'd find that many people have said this idea and nobody has either built one, or even attempted.
1. Ghasts would spawn, creating havoc and in the end, just ruining the games completely.
2. It would be too much like the regular nether. A spawned world that almost ALL minecrafters have played in, and would become boring very quickly.
3. Dying too quickly. People would fall into lava, hit a zombie pigmen on accident, or be struck by a ghast. Therefore defeating the actual purpose of the map PvP.
I'm sorry, but it just won't work.