Some Halo 4 modder, made this mod a while back where your player model is immune it any death barriers. I haven't seen anyone really do anything cool with this mod so I forged a few maps so players can get out of the maps without having to return to the battle field. The out of maps in Multiplayer are significantly larger than any on Campaign.
http://www.youtube.com/watch?v=jBTFtLTwXxQ