That's interesting. Some people want a trailer just for sleeping, but cook outside and use the CG restroom. You're thinking of the exact opposite! :D We're all different.
I can't think of any units built specifically like that. I doubt you will find a TT with kitchen and bath but no place to sleep. However, one could buy nearly any trailer and then rig up a stand-alone tent or shelter in such a way that it attached on one side to the TT. Some tents are fairly upright in shape; you might have to cut one end and add velcro, snaps, or whatnot to fix it to the trailer.
I think your best bet would be to buy a small cargo trailer with rear ramp door and build (or have built) some kitchen cabinets, a cooktop, a bathroom, electric wiring, and holding tanks. Also add another rear wall with conventional rv door about 1 foot inside of the ramp. Add a tent that attaches to the large rear (cargo) doorway and rests upon the ramp when the ramp is open (but level, with end supports); perhaps one of those tents that fit onto the back of an SUV would work without much modification. That way you still have 4 hard walls, plus a tent that is off the ground!
I actually gave some thought to using a cargo trailer for camping, only my idea was to get double rear doors and to use screen material across the entire rear doorway. I would still sleep in the trailer, though. With this rig I could open the big doors for the breeze, scenery, etc. and still be able to close the doors whenever I wished (bad weather, privacy), plus have no canvas to get wet.
