Good points, had not given consideration to the potential low flowrate whilst just on a filter cycle, mine has a two speed pump, will check the flowrates via the manufacturers datasheets.
From my understanding with the Balboa system you keep the heating element in place as it has sensors at each end of the heater tube, but you disconnect the heater plug from the PCB, i've seen two configurations, either using the Balboa PCB to power the heat pump, not prefered option imho, or power the heat pump standalone which is probably my prefered option.
Will do some more research and update here if i go ahead.