Back in the nineties, I had a 1960 C172A, lived on a grass strip west of Baltimore (1W5), and commuted to Silicon Valley for a week about once a month. The trick was that on Sunday evening I flew down to IAD to catch the 6pm UA 747 to SJC, and returned on the red-eye Saturday morning. It was pretty comfortable in the upstairs deck. For east coast trips I flew the 172, with door-to-door times comparable to the commuters, unless there happened to be a non-stop. Even twenty years ago, the seat in an elderly 172 was more comfortable than those in the cigar-tubes.
I suggest the FAA start with a modern C182 (or Cirrus, or comparable GA seat) and require that no airliner seat be more uncomfortable than that.