When I first saw 42156 described as a vehicle and its price, I got excited that we might finaly get a proper fire truck/fire engine. A lot of MOCs out there showing it can be done and that it would nicely fit in with the rest of the trucks.
Take Fire Truck MOC from time-hh on rebrickable for example. I think that it's showing great potential at this scale and the model could also include some "accessories", like 42139s chainsaw. The jaws of life maybe...
The gearbox could be integrated in such set. Controling outriggers, ladder (extension and rotation) and turntable all from one input. Maybe even some panel "doors" to show the equipment and the details.