I'm still using Bongos2, but is there a reason it won't work for your purpose?
I had planned on doing the same thing - lay out the action buttons based on the X-Keys I purchase, and there are plenty of bars to accomplish this.. since you'll only need 7 for the X-Keys Pro - just leave blank buttons for the space between keys, and space the top two rows a little away from the bottom 3 button groups.
That's still 3 more bars available for the rest of your commands.. is 10 bars not enough?