I've probably over complicated things, but that would be me all over.
I only have ALS ambulances so that was easy, however, as I have tried to recreate my fire stations as close as possible to real life, some have full size engines (currently all rescue engines) and some also have type 2 engines which are normally just a 4x4 or equivalent.
As i'm using rescue engines throughout, I don't have to worry about the firetruck/heavy rescue issue but to allow me to send a type 2 whenever I didn't need the heavy rescue capability, brush fire, wildfire, etc. I gave the type 2 engines their own type of 'Light' and created a separate AAR for them.
This way, if I just need a fire truck, I can send one, but if I need a heavy rescue I can send a full size engine.
I have done the same with K9 and patrols.
It adds extra to the AAR but using the time to incident option, I can also see what is closest.
Hope this helps.