Chris,
The difference between Pitch and FPA certainly gives a rough guide to AoA, particularly changes of AoA. As has been said by others, it should be correct in still air, but becomes increasingly inaccurate as the headwind or tailwind component increases. That's because FPA is in relation to the earth, not the airmass. (So vertical movement of the airmass, particularly a microburst, will also cause inaccuracy.)
Thanks for that, that's cleared up the confusion for me.
Regarding turbulent air, mictorbursts etc. I imagine one would experience large transient changes which I don't think would be particularly useful. The rise and fall of the barbers pole would probably provide the best awareness or critical AoA and given that TOGA FD guidance will attempt to maximise climb performance possibly at intermittent stall warnings averting one's gaze to an AoA indicator would probably not be all that helpful.
We have the AoA indicator on he HGS (737). But then we know what power settings and pitch attitude combination to use. Without specific practice/training on adjusting speed and pitch with sole reference to the AoA would anybody actually use it? Maybe as a crosscheck as long as you it doesn't then become confusing in an unusual situation.