im trying to keep it slightly less complicated. i understand what your saying but i think due to the amount of differences trough out the USA let alone the world and not to mention the game play balances
a way to see it is in america you can walk up to a pierce dash engine in LA and walk up to one in Miami the differences are huge because the way the US fire services are you would have so many options for pumps tank sizes crew arrangements layouts ect
i know here in Australia mainly NSW almost all full time fire trucks have about the same pump size same tank size and same layout(per type of truck)
and the volunteer fire service have the same layout on every truck