Slightly OT, sorry:
OpenOffice.org does allow you to attach an XSLT stylesheet to an export process which therefore allows you to do a (limited) transformation from the visual markup which is its native format to a more structured one
Why „limited“?
Well, XSLT seems to have been designed, and certainly tends to be implemented, as a tool for simple transformations of small XML chunks. Obviously complex transformations can be constructed from a bunch of simple transformations, but there comes a point when you should really just use a better tool - though these tend to cost serious money (e.g. OmniMark). Also, most XSLT implementations use the DOM model, which is fine for a 50Kb file but will be incredibly resource-hungry if you're processing files of 5Mb. At that point you want a streaming model, and for a streaming model you want a better suited language than XSLT. As I say, horses for courses. For article-length pieces and simple transforms, XSLT might suffice.
Also, don't limit your authors to Word. Offering Word is obviously a requirement, but if you go the way through OOo, there would be no point in not offering an OOo template file. If you are using a standard xml format, such as (a subset of) DocBook or TEI, you probably should accept articles in that format, too. And, of course, ConTeXt.
Absolutely; particularly if you can offer authors an incentive or direct benefit from adopting OO.o, such as speed of turnaround of proofs, etc.