Its a nice idea Steve, but if this is CNC for beginners then my 2p is that this complicates things - the device you show is still only a controller, you still need the stepper drivers, and I would argue most who are interested in building a CNC machine have access to a PC.

I think concentrating the electronics side on either sourcing a cheap driver set or, complementing the intent of the design, a cheap, easy to build, set of drivers would be better value. There is a wealth of knowledge about EMC and MACH3 and, esp in the case of EMC, there are a lot of cheap PC available to run the free software. Indeed, for real low cost, EMC2 (free) on a PC sourced from eBay has got to be a better option - there's a good selection of P3 and P4 systems which would run EMC available for <£100 and some as low as £30.