I don't know whether an IWL16 display board will mate to a Phase 6 motor board. It won't if the boards are digitally coded to match. I don't know if damage will occur on a mis-match or if the machine just won't work.
Swapping in a Phase 7 stator & rotor along with a Phase 7 ECO* motor board and suitable display board may be doable. The Phase 6 off-balance microswitch is eliminated on Phase 7 so there's nowhere to connect it on a Phase 7 board. Phase 7 (and higher) off-balance detection is via software monitoring of rotational feedback through the RPS. Phase 7 inlet valve assembly is different with the temp thermistor relocated but the electrical characteristics of the solenoids is the same.
*An AquaSmart motor board will not work, it cannot run the standard Eco pump and diverter valve. AquaSmart has a completely different 3-phase reversible pump, no diverter valve. Phase 7 AquaSmart also has a different basket size/weight and different tub suspension rods than EcoSmart.