Small Mill very early design stage

[leadinglights]

At the moment my new machine is in a very early design stage: it was quite far advanced until I started asking questions on this forum and found that many of the things I was going to do wouldn't work, so at the moment even the basic architecture is in the air.
The eventual aim is to make a milling machine to make very small parts in anything from machinable wax to steel. The main requirements are accuracy, accuracy and more accuracy. Something slightly bigger than my existing Proxxon MF70 would be nice - a Y axis limited to 40mm is a bit of a drag, but 200mm by 200mm with enough space in the Z axis to allow 4th and even 5th axis work (eventually) would cover everything I want to make.
I am impatiently waiting for some linear guides that I bough on ebay to arrive so I can start serious design work - the manufacturer's site does not have datasheets for the ones I bought. Meanwhile I have attached some JPEGs, A formation of components done in Turbocad - mostly not applicable, I am (probably) not using round rail, the toothed pulley data was taken from an RS datasheet which was just plain wrong. The second photo is of a 218W brushless DC motor from Zapp, along with a controller that I built - PCB made on the Proxxon. Since that photo I have had the motor drive a spindle at 55,000RPM.