Hard way? Pretty simple for me. Splicing in 2 tees, adding pump between the hot & cold lines at the only place I have access. I do not know how it could be simpler, my convoluted wiring withstanding.. Not sure I'm following,
What you described would be painful if possible in our truck camper. Running another length of pipe, certainly wouldn't be easier. If it were you could run line back to the fresh water tank, that would be the simplest, not even use extra pump just a valve. Back side of water heater is virtually inaccessible. However IF you added a tee just before the water heater in the cold line-wouldn't you be duplicating what I did? cold tee could be anywhere.
But theres a dozen ways this could be and is done.
