I've wanted to do this for a while, and now I think everything is finally in place for a small run of semi-custom 650B randonneurs. Five to be exact, to be built this winter and ready in spring. They will be available as a frame and fork or complete bicycle. See my flickr page to follow the progress: http://www.flickr.com/photos/mapcycles/sets/72157622852473295/
Each will be custom in that they will have a rider-chosen seat tube and top tube length (within the 54-58cm range) and each will have the opportunity to add custom MAP handlebar bag rack or small rear rack as part of the package. There will be a few other options in terms of braze-on placement and paint, but the heart and soul will remain the same. Light weight standard diameter tubing, proven rando geometry, and clearance for big 650B tires.
There are a lot of details to go over in terms of the build possibilities and packages, geometry, paint options, etc. that I am not going to go into here and now, but for any interested parties, head over to http://www.mapbicycles.com/news.html and come January, I'll provide all the details about just what this bike is and what it is not and how you can get one. Cost for a the frame and fork with single color finish will start at $2000.
For now, have a look at the prototype to get an idea of where this is going.