I honestly wouldn't mind GEMA maps as much if they weren't so, well, amateur-looking. It's hard to take a map very seriously when it has nothing but one tile texture and 256 different colored lights. I remember there was one GEMA-style map in the original Cube game that managed to look and feel professional. If there were more maps like it, then I might actually be in favor of a native GEMA mode.
EDIT: here it is
EDIT: here it is