If you remove the bed on the side with just the storage. I'm guessing there are cabinets above it. Which means you would need to remove the cabinets as well to provide a walkway around a wider bed on the side with the HVAC/Plumbing under it.
Our first TT had twin couches at the front. There was a sliding extension under the seating area of each couch. You slid the two extension together to form a larger than king size bed. The couch cushions became the mattress for the bed. The sliding extension was basically a Plywood platform with a wall on one end to provide support when extended.
You could use the sliding extension idea to make the remaining twin bed wider and then use a futon mattress or Aerobed mattress