Yes, RefTeX's job is just to insert a \cite{BibTeX_key} command. It doesn't care what the major mode is when you call it. And though I sympathize with the reasons not to use LaTeX for academic writing in the humanities (since few potential colaborators do, and publishers hardly ever will), recent developments in the BibTeX realm have reduced the problems there. If you haven't seen
BibLaTeX, have a look at it, it's a BibTeX replacement with much more flexibility. There are already a few interesting citation engines build on top of it:
biblatex-chicago, which I use and am happy with (it's in-progress, but in very active development), and another
biblatex style for historians (which I can't speak to.)
The whole process of exporting a document of any complexity to MS Word format sounds daunting, but I'm glad to hear that others have had some success with it. Many thanks for starting this thread. I've learned a lot.
Scot