So IRL there are different fire engines for different purposes. my idea is that several vehicles should have special ability's and carry special equipment.
So here is my idea, add either new vehicles or add upgrades to be purchased for the vehicle.
Change The Name Of The Water Ladder To Water Ladder + 13.5m
So this vehicle would carry the 13.5 meter ladder and primarily carries general firefighting Equipment. this responds as a smaller version of an Aerial Appliance and with say 3 or so Water Ladder + 13.5m Fire Engines could sub-in as an Aerial Appliance. Like IRL the 13.5m ladder is only carried on Pump Ladders, however they have a 1,800 Litre Water Tank.
Add A new vehicle called Water Ladder + 9m
so this vehicle would carry the 9 meter ladder and primarily carries general firefighting Equipment. this responds as a smaller version of an Water Carrier and with say 3 or so Water Ladder + 9m Fire Engines could sub-in as an Water Carrier. Like IRL the 9m ladder is only carried on Pumps, however they have a 1,800 Litre Water Tank, With a booster Tank of a Further 400 Litres.
Add A New vehicle Called Dual Purpose Ladder
This carries both the 13.5m Ladder & 9m Ladder and Carries a 2,000 Litre Water Tank. Acts and covers both the two above.