Take the last section off the tank, put a pump unit and hose reel back there, extend the front bumper, put a small pedestal/tractor seat on the right side front with a short hose, tool boxes down both sides of the tank and you'll have the trucks we use here at my department.
Thanks for the idea! Would you be able to snap some pics covering 360 degrees of the truck? That way I can make it more prototypical.