I've been looking at this:
From the drawings I've seen the Lunar Gemini might be just that, the capsule on top of the LEM's base. It makes sense, and all parts seem to go in the right places.
I know that there would be a mirror installed in front of one of the Gemini's windows so that the astronaut could see the lunar surface...
Something like this is can be done, and we already have the meshes for it. The main problem might be the surface EVA.
One thing that I can't understand form the documents I've read is the Earth return. How does the Gemini capsule lift of from the Moon? Is the service module modified so that it has a engine? I don't think there's enough room in there for it and supplies for an extended mission.
Any thoughts on doing something like this?