Its not just those two jimmy, its the DA as well, heck you could even extend it to the scenario/AvA arenas if they made the arena browsing GUI simpler.
If HTC did such a move and were kind, they would simply provide settings templates for custom arenas to allow you and the other guys to re-create the MW/EW arena and maybe you can play with other game modes as well to make something that might actually be cooler then the LW, who knows?
But without said modifications how would that be any different from what you have now?
I might be wrong but I believe all available terrains are usable in the custom rooms. I know I have used the DA one before.
The added bonus to creating and hosting your own terrain in the custom rooms is that you can setup the environment however which way you choose. I've only seen a handful of people utilise this great feature though. Any squad training we do is done with our custom maps.
I've been looking at new event ideas we could use them for with really neat terrains designed for the purpose but and this is a big but. Having gone to all that effort would the player base actually bother to logout of the MA carry on and have some different type of fun.
With the attempts at sdl, a multi squadron team event and a dogfighters club all of them seem to die out eventually