It should have all of the items either in the bleachers/stands/whatchacallit, and in the rooms underneath that lead to the arena. The aforementioned rooms should also be closed off from everything else, so that the Predator monsters don't get anywhere else. Players could be in the stadium seats watching the Predators and Titans kill each other off, or jump in if they wanted to.
Only problem is the Titans can jump high, and would get on the stands and attack the spectators. Someone needs to make a Q3 mod with monsters that you can place like in Jedi Academy, because I see a lot of custom Quake 3 maps on here that would make for nice Co-Op maps.
Edited 11 seconds after the original posting.
...........Ok maybe not
Damn shame, 'cuz the layout isn't bad.
Texturing reminds me more of a flat quake map from "back then" ;)
Learn how to alter the light values of the shaders connected to the sky textures and spend a bit more time on the basic textureing and this could be real good.