Eric, nice post !! I totally agree that TSA is the biggest problem.
I still used a hard case, but have found a couple of helpful ideas worth looking into.
One is to mail the bike, expensive for overseas...yes, but not had a single issue with customs, or getting the bike to the hotel. Last time I used luggage forward, and they were much cheaper than Bike Flights, for overseas, but that may have changed. For PBP 2019, I took the bike on the plane with me, but mailed a big box of heavy drink mix powders, tools and bars, to the hotel, to help keep the weight down, keep the bike box from being overweight, and free up an arm, as I could have lived with out anything in the box, if I needed to.
Just home from a domestic trip, and used Trico Sports hardshell and it worked perfectly, in large part I’d guess, because I did not put anything in the bullet proof bike box except the bike, clear water bottles and a helmet, so TSA just had to lift the top off look and close it back up. For sure did not leave the seat pouch in the bike box. I’d agree that the Trico Sports hardshell takes an arm, to pull it along, but in this case that was not a bad thing, as I could sit my duffel bag on top of it and roll it from the BART Station to the hotel, down the sidewalk with out too much trouble, for that long of a walk, my shoulders were already worn out with the full back pack.
No one right answer for sure, just more options to investigate and think about.