Ahh, much comments are coming to you about using your own pieces. Most of these pieces are buildings Bungie made already. But on to your map, you should take out the warthog, there isn't any space for a warthog to be driving around. Also what is up with the gravity lifts in the center? It's just a suicide trap or infinite jumping.
Yeah, gotta agree with Shikarix. Main problem, premade buildings. If you want to keep the Warthogs, I'd suggest moving the map to the Canyon or Montana.