Kinda impractical except for the Square box motor coaches. I saw a SOB with a murphy bed not all that long ago, but i literally pulled down over the sofa in the living room.
The old "Gauchos" seem to have been made with the express purpose of making you yell "OUCH-O" every time you rolled over the lumpy seat or back and fell into the split!
I'm not surprised to see a lot of futons replace some of the remarkably lumpy variations of the sleeper sofas - which are torture devices in both configurations. A GOOD futon is probably a nice choice for a Trailer... and it's easy to get in through the door.
Even the Dinette conversion leaves a lot to be desired. first you need some kind of non-skid material to keep the cushions from sliding around on the table portion - and ye Gods, why does the table always have to protrude 2 inches beyond the cushion? Just to remove the skin from your shins as you enter? Next the cushions (except perhaps on the Classic) are thin. A mattress topper or comforter helps, but where do you store the darned thing? Adding an air mattress on top of the cushions makes the dinette bed a bit high to sleep in.
I've always thought it would be nice to have a pull around curtain so that the sleeper in the dinette or couch would have a tiny bit more privacy - and so that I could turn on the light to get a bottle of water or use the bathroom without disturbing a guest.
Today is a gift, that's why they call it the present.