Your not missing anything, the weapons code is unfinished, there is no DeHackED support, no BOOM support, and finally, no MOD support.
Personally, I'd find a copy of Linux for the XBOX, and run DOOM Legacy or ZDOOM (if you can get the damn sound to work) in software mode on there, you'll be MUCH happier, well except for the fact that none of the guys doing XBOX Linux have configured the Joypad to work decently in 3D games, though they are sooooo close.