Started a new project…
I am using an Arduino Due as the brains for this. I chose the Due for 2 reasons, First, it emulates a USB keyboard very easily and second, I had one not being used 
The buttons are wired into a 4 x 7 keyboard matrix, so I have 28 buttons. I will take it all apart, build a box for this to sit on and house the Due and the wiring and paint it.
I decided to go wired as I don’t tend to wander around too much while working. This will sit in front of the X-Carve on the stand.
Everything is wired up and the program is written. All the buttons work great and control the machine through UGS.
The only button that I haven’t gotten to work is the Abort button, UGS has no way (that I can find) to send a CTRL-X to the machine.
@MechanicalGoose - How is your abort button configured?
@WillWinder - Is there a way to send CTRL - X through UGS to the controller?