Made some good progress with dm5rmx. Will probably refine the lighting and brushwork a little more, but it's pretty much done. Working on gameplay at the moment (probably should have done this FIRST)
http://i.imgur.com/vU5eK.jpg
TL: dual layer corridor top
TR: dual layer corridor bottom
BL: inside the cistern
BR: one of the new areas
dmr3rmx is still the closest conversion I've done. I think it will probably stay that way; This one is pretty different beyond the original layout still existing amongst all the new stuff.
I tried to give the feeling of bounced light a lot on this map, so I used quite a lot of low intensity lights with falloff values set between 0.125 and 0.5 to eliminate hard black shadows where they felt unnatural. Still don't want to use coloured light though :)