Some points and answers:
Engine rollback is fixed; all engines are modified.
Unpressurized flight is allowed up to (and above) the crew cert limit of 14,000 ft with O2, but keep the icing and air systems for high-level transit.
The aircraft is a delight to fly, convert the fire-fighters, they will probably find new techniques available from the high turn rates at low speed and a good wing-over capability.
The original design for the aircraft did not have an APU. Double battery start mod is available for starting an outboard engine, then use electric cross-start for the others.