My build/idea images are posted to this link. https://picasaweb.google.com/108335829480258795541/TinyToyHauler#
I can use 4' high sidewalls, by removing my quick detach windshield and rolling the handle bars down.
Overall box length will be 10' plus the rear hatch. Hatch stays up to form hard porch roof and is of a box design so that awning fabric and poles will stow inside the hatch.
So the box structure is basically 4'Hx10'Lx5'W.
I will use a pulley and cable system in the roof/ceiling to get the bike in and out, with commercially available aluminum ramp.
Wheel dock will be bolted to floor in front.
True queen size air mattress will sit on a raised box foundation like the dinette in any commercially produced RV or camp trailer, the center will be just a sheet of removable plywood
I will use an adjustable tongue tube to account for varying CG/tongue weight, depending on bike loaded or not.
There is ample room for a small AC unit or heater. There will be no galley, as we generally cook on a picnic table even when fifth wheeling.
All the places we stay have full facilities, so we are up in the air on the Hygiene related amenities.
You may want to look at a plywood boat building method, that may come in handy on my build. It's called Stitch & Glue. Makes a very lightweight and STRONG boat.
https://www.google.com/webhp?sourceid=chrome-instant&ie=UTF-8&ion=1#hl=en&sclient=psy-ab&q=stitch%20%26%20glue%20boat%20building&oq=&gs_l=&pbx=1&fp=327738fe10fbc33&bpcl=35277026&ion=1&bav=on.2,or.r_gc.r_pw.r_cp.r_qf.&biw=994&bih=606
Good luck. My build has begun 4 years later than planned. But I now have a firm vision and foundation, ie: a Harbor Freight trailer

Jim