Nice looking rig! Under My RV, I have a box around my pump and valve assembly. When I have hookups in sub-freezing weather, I have a single bulb 12V light that is left on 24/7... It's enough in that small space to keep the pump from freezing.
A close friend has his waste tanks exposed, with a gap in between. The plan there is to spray-glue and double layer reflectix them, and install a light in the gap, which will be covered but accessible.