Don't you think that implementing the MoH:AA BSP format into Horde3D would be a nice idea?
It's much better than the old Quake3 format, many improvements have been made (bigger maps etc).
It's already available in OMOHAA project (
http://openmohaa.sourceforge.net/) - open-sourced, GPL-ed and based on released on Q3 sources.
In the past I was working on some maps for Q3Engine based games (Q3A, RTCW, MoH:AA, CoD) and I really liked the GTKRadiant map editor (also GNU GPL). Hope someone finds this idea worth considering.