Unfortunately I'm going to bet your front wall is the same Styrofoam as the rear making it impossible to just push a wire through. What gauge wiring are you running down the wall? Can you hide it on the surface behind some white or tan channeling?
LinkIt looks like you have cabinets on either side of the trailer that comes down most of the front wall. And I'm assuming there's a night stand table feature under the cabinets leaving a gap between the two of about maybe 18 inches. I would take the voltage drop hit and extend the wire over to the drivers side front corner and come down inside the cabinet. Then it's only a short run of visually exposed channel under the cabinet to the night stand and then across to the batteries. I'll bet after a week you wont even notice the channeling unless you actively remind yourself it's there and look at it.
You could even put something in front of the exposed channel like a framed picture of the family or a vase of silk flowers velcroed down so it doesn't move during travel.
