Short answer appears to be that it might be feasible given the fact that both systems have mostly the same components.
The both have an electronic servo assembly, actuator cable, horn relay, steering wheel switches, a brake-lamp switch and a deactivator switch but the AU also has an RHS Combination Switch not present in the earlier ones but all it does electrically is replace the 'ON' switch of the earlier model.
The servo is mounted in the engine compartment near the brake booster, and is connected to the throttle linkage with an actuator cable. The electronics are integrated in to the servo, eliminating the need for any electronic modules in the vehicle on both models.
Deactivator switch is located at the port of the master cylinder proportioning valve on both models.
Looking at the wiring schematics they looks to be largely identical except for the different method of turning it on but that should be easy enough to re-wire.
The 10 pin connector at the servo is slightly different as per the table below but only in how the 'CRUISE ON' signal gets transmitted to the cluster.
The two wiring schematics are below:
EF/EL
AU
