I have a few thoughts on this. Hopefully what you're looking for is honest feedback.
Overall accuracy is different than repeatability, and both of these have as much to do with your transmission components (belts, screws, rack & pinion) as your frame.
It should be noted, that there are people that have spent big bucks on profile or linear rails with linear bearings and have precision machined components on a precision aligned frame and aren't getting anywhere near the 0.1mm accuracy you're looking for, especially at the size you're looking at.
As a rule of thumb, a generally descent ball screw might have an accuracy of 0.003" per foot. You're looking for this for your whole system. Belts stretch, rack and pinions have backlash...
My point is that I think you have expectations pretty high. The beauty of wood is that there's sandpaper for the fine tuning of mating parts. You'll probably need to compromise your accuracy requirements or your budget. That choice is up to you.
Good luck!
Matt
Matt Adams - Motion Control Application Engineer
IMAC Motion Control - Elgin, IL