Salute Concours!
Yep, if you have a fixed reference in the display, HUD or FD, the AoA is the difference between the "bird" and that reference WRT the longitudianl axis of the jet. Sure, the wing chordline versus the fuselage axis must be allowed for, but on some planes this is a fairly easy thing to do.
I flew HUD planes with great velocity vector displays and those were extremely useful for establishing glide path or descent angle or..... The AoA display was only constantly presented on the HUD or "indexers" or even a steam gauge in two of the jets ( about 1400 hours). The biggest use of the AoA, besides knowing you were approaching stall, was approach to landing. The approach AoA took into account your weight!!! So a quick, rough calculation we used in other planes was good, but that AoA was the real deal. E.g. "approach speed is 175 kias plus 5 knots for every 1,000 pounds above 3,000 pounds", I leave it to the reader to figure out what that plane was, heh heh. I was USAF, but the USN used AoA a whole lot more for landing on a carrier deck, and USAF was more "airspeed" on approach than AoA.
All that being said, use of AoA by the crew for most flight regimes requires some training and rationale. My vote would be what I used it for - approach speed and stall warning. Oh well, enuf philosophy.
Gums...