So I came up with a solution, based on the rather expensive, but now defunct Open Labs Neko.
Dual Pentium G840, Mini ITX MoBo, 4Gb RAM, 2 x 120Gb SSD, PCI Firewire/USB card, all built into a 1U server case, running Windows 8.1, which in turn is built into an MDF/Tolex case along with my old Firewire/ADAT interfaces rescued from oblivion (I had to stop using them when support for OSX was dropped).
The monitor is a 23" HP 23TM touch screen, and it's all run via Image Line's Minihost Modular.
Everything in the studio is hooked up to the FW interface (16 analogue inputs, 12 outputs) which are available on screen via yellow "tabs", these can be patched through to whatever output, even through VST FX if you want. Softsynths can be dragged and dropped into the virtual studio and all edited with the touch screen then sent out via my USB mixer to Logic running on the Mac.
This is exactly the Synth I've waited for, the Kronos comes close, but obviously there's no support for 3rd party software.

More pics:
https://www.flickr.com/photos/arp2600cl ... 2843006998