Can water heater run while towing? Here's why . . .

So, your plan is to circulate water out of the potable tank thru thr water heater? I assume your plannjng on some sort of bypass so your not trying to use hot water all the time.
Can it be done? Sure, anything is possible. Will the WH keep running and not blow out going down the road? Maybe, maybe not. Likely it will blow out, or burn a lot of propane trying to get all that water hot.