If you are building a VMC then why restrict yourself with a Myford type spindle.
If you already had one, I could understand your philosophy however, you are limiting yourself to an MT2 spindle and a nose thread that really does not lend itself to milling operation.
If you are scratch building, I would suggest you investigate an R8 type spindle, these are available ready made for the Mini Mill, from Little machine shop for a very reasonable cost (although shipping and import can be a killer)
Failing that, A competent machine shop (or someone here) could produce a spindle for you. Or you could make yourself -looking at your profile I would suggest this is well within your capabilities.
Having had MT taper based mills in the past, I would never go there again, R8, or Int30/40 taper would be my choice for many reasons.
Just my tuppence to add to your thought process 
regards
Graeme