Andrew, sorry if I'm way off the mark as you are way more clued up about this stuff than me, but is an Xbox controller no use. I use one and I am sure PhilF uses one as well. Just a thought.
I do use an Xbox controller with no problems. I've got mine configured with X, Y, Z & A as well as Start, EStop, Auto Z height, Spindle On/Off. Beware non-genuine controllers. My first one looked the part but would give random movements after a few months use. I've had no problems at all with my genuine Microsoft controller.
I also use another device for very fine movements e.g. when using a wobbler to find a datum. It's a video editing device and has a wheel which replicates a dial on a machine except that you can change the resolution for fast or fine movements. Mine is a Contour Shuttle XPress.
Mach3 provide a plug-in for both.
Both mine are USB. I didn't like the idea of wireless as it's best to have as little as possible other than Mach3 running on the PC.