Functionally, that's a nearly ideal setup.
The only potentuial problem is that without the OEM combination valve, you won't have a brake system failure warning light. The light in the dash will continue to function for the parking brake, but won't signal a loss of front or rear brakes. Personally, I can tell when one circuit blows -- don't need the stupid light to tell me.
But ... I don't know if there are any laws prohibiting removal. My suggestion would be to keep the combo valve so you can reinstall it if you ever sell the vehicle. Or, leave the stock combo valve in place, plug the outlet on the bottom that feeds the rear brakes, and run the rear line from the "nose" of the combo valve to the Wilwood proportioning valve. You'll have the same functionality, but you'll still have a warning light.