After studying this for a week or so, I took the plunge and started to build up my homebuilt minivelo from junk bike parts. I started thinking that I wanted to build a bike that could easily be put in a suitcase by using sleeves as referenced in another thread, and I still intend to do that. But I decided I would build it up this way first just to make sure I like the ride before I cut the frame.
Here is where I'm at now. It will be a 52 chainring/16 freewheel single speed bike with front and possibly rear caliper brakes. I figure the less stuff I add to it the easier it will be to pack. I know the handlebars will probably have to be dropped some more.