Is the problem with compatibility with the standards relating to intruder alarms showing the zone, or inclusion of fire alarm functionality?
BS5839-6:2019 seems to be quite positive about the safety advantages of grade C systems over grade D systems, and specifically mentions that grade C systems can be integrated into intruder alarm systems. So, I'm not sure that a grade C system following BS5839-6 incorporated into an intruder alarm is inherently dangerous. However, with the i-onG2SM at least, there do seem to be some difficulties in following all of the recommendations for grade C systems in BS5839-6 using an intruder alarm.
I completely agree about not wanting to have to use the keypad in a fire situation, which is why I had hoped there was a way to automatically display the fire zones (as is required for a grade A fire panels). In my particular situation, a night time fire (or intruder) alarm in the detached garage would need a different response from one in the kitchen, so being quickly aware of the alarm location from the landing RKP would be very helpful.