Probably the biggest problem is that the Air Suspension Control Module (ASM) will still be required to operate the rear air springs and ECATS adaptive dampers, but with the front air springs no longer connected it will trigger the AIR SUSPENSION FAULT and CATS FAULT warnings on the instrument cluster and may possibly go into hard fault mode in which it will no longer operate the rear air springs. To overcome these issues, you will need to "fool" the ASM into thinking the front units are still attached. Somewhere in this forum 34by151 describes how to bypass the height sensor wires at the ASM with 10K potentiometers to dial in the resistance that results in the correct ride height. I can't recall whether he figured out how to simulate the ECATS solenoid coil with a simple DC resistance, but since the solenoid is driven by a 400Hz PWM signal, it may be more complicated than that.

Cheers,

Don