In at least the US version, we should have LESS fires and more calls. The ALS Fire Engine is annoying. Everyone knows that a real Fire Truck wouldn't transport. Here's what I think.
Engines and Platform Trucks should double as Fly Cars.
More calls like (CPR, Unknown Medical, etc.)
Maybe even fire alarm activations, Lift Assist, and the like. It's really hard when several major missions stack up, consuming every last resource.