Tiny conversion for tiny work; Denford Micromill 2000

[TinyWork]

Hello, this is my first post and I'm about to receive my first CNC mill – a Denford Micromill 2000.

Being old (but not quite obsolete) I would like to upgrade it with modern electronics and a wider choice of operating software. Denford are quoting an eye-watering price for upgrading the internals and software, so I thought I'd spec it myself, and maybe end up with a better machine than you can currently purchase from Denford. I plan to strip out the internal hardware entirely and start again.

So far I have the mill (2002 vintage) which is in very good condition, only seeing occasional and light work – I don't believe it has cut any metal at all. It's a good candidate for upgrading as I don't have to refurb any parts of the mill itself. I'm going to use it for producing small aluminium tooling for an benchtop injection moulding machine, so it has to be as precise as possible. It will be run directly from a SolidWorks plug-in.

In addition to the mill I have also ordered a slightly used Leadshine MX3660 driver and I will shortly be ordering the two power supplies and the excellent Centroid Acorn controller. I'll keep the attached stepper motors, spindle controller and spindle for now, but I will want to upgrade the spindle to a faster type soon. If anyone has any suggestions for a compatible 20-30k rpm spindle I would appreciate it.

I think I've attached a basic schematic of the upgrade. Your views and suggests are very welcome.
Steve