Anything is doable. It looks like a lot of work and having it match, could be very difficult. It looks like the sofa is alone an inside wall with an opening. The wall would have to be opened up and reinforced. A lot of work. We had a tt when I was a kid where an overhead cabinet along the front of the tt, that converted to a bed. Basically the cabinet front folded down, and landed on a few metal tabs on each of the side walls.
Here's another option, how about a tent? It would give him lots of independence. Get an air mattress to sleep on, maybe an extension cord for a fan.