Battery rearrangement

Where is the wire that goes from the starting batteries to the engine? If it doesn't also connect at the solenoid, you won't be able to switch them around simply by rearranging connections at or near the solenoid. You need the connection from the starting batteries (wherever they are) to the engine systems on one side of the solenoid, and the connection from the house batteries to the house systems--which often for Coachmen RVs seems to be via a little bus bar with a few self-resetting circuit breakers attached to it--on the other side. There should be some sort of overall overcurrent protection close to each of the batteries to help prevent a fire in case the cable from the battery to the systems should chafe and short out or some similar catastrophe occur.

Frankly, if the existing setup is working fine (the engine starts reliably, etc.), I don't see any real reason to change things around, even if it logically seems theoretically when differently arranged.