If you would like to keep it simple, you could try what we have done, prior to making any modifications to your trailer. We purchased 2 back-packers self inflating air pads (small/short ones by ALPS Mountaineering) and simply placed them under the original Scamp
pads, beneath your torso. I was sceptical that something so small and thin, could do anything, but they really work! We just spent 2 months living/traveling and had none of the usual arthritic back aches. When you want to use the bed as a table, the cushions simply fit under the seat cushions or you could roll them up a stow them away. You can keep your bunk/couch up front and use folding/tv tray/tables when eating, and enjoy the couch for reading or the bunks for the grand-kids.
If this doesn't work, you could then spend the time & expense of the other very nice modifications.