I have come to a similar conclusion about the ideal travel bike. Someday when I need one more, and have more money, I would like to get a Bike Friday custom job with a fixed/free hub and a front brake.

I'm in the midst of converting my 2001 Dahon speed 7 to a single. Should fix the chainring jump once and for all!

Have you thought about either buying a bike you like and converting it, or talking to the manufacturer about converting it for you? seems like it would bring the price down, unless the "custom" nature of it was too...heavy or something. Converting to single is largely the removal of parts, so I can't imagine it'd be too complicated.