I used have used my Dive Caddy backpack with no issue, as recently as late July of this year on a trip to Grenada.
TSA (flying from Detroit) had no issue in either direction.
Fit in the overhead bin quite nicely.
In my experience, most TSA agents recognize dive gear quickly and have no problem with it. Only once did I have a newbie that was confused by my reg set on the Xray. On that occasion, they opened the bag, saw the regs and closed it within a second or so. No significant delay.
Safe to say that wearing the BCD as a vest through TSA inspection will not work. They will ask for it to be removed and Xray-ed (like a jacket), but should be able to be donned again for boarding the plane.