Heya, I've been reading through the topic and I noticed nobody seems to have stepped up to the challenge of making the maps yet. I've always found the DOS stages funny for their quirky level design and being generally weird. (Water level for Torch Man, anyone?) So I would enjoy making a few maps for this expansion.
However, I haven't done any level design for an FPS game before. Although I have done some map making for games built with the Doom Engine. To be more specific, SRB2, a Sonic platformer.
http://www.youtube.com/watch?v=Z913jWnUrtw <-- delicious example of my work, you must watch it.
I would need to get the required software for standard Doom editing etc and I would need to get to grips with a different style of level design. But I'm still willing to give it a try. (Perhaps more importantly, because MM8BDM maps are so much smaller than SRB2 maps, it won't take months to finish something

)
Also, if the dialogue for the Robot Masters hasn't been created yet, I would be happy to make a few suggestions.