The only substantial argument against across the board AoA adoption I have read here today is the one about it being a cockpit distraction. All the other ideas are problems that can be solved or mitigated. The military does not find it much of a cockpit distraction from what I understand, and going out on a limb a little bit I think if you require AoA in all new primary training aircraft and thoroughly revamp the FAA primary pilot training liturgy the same way it was revamped for glass cockpits a few year ago, you could remove a lot of distracting material and replace it with AoA awareness techniques in lieu of a bunch of other training tasks. At any rate, tests can be done with and without the AoA instruments in ground sim to see whether they are distracting or not.

I would vote for a suite of 4 gauges rather than one, because until you know left & right AoA values for both tail and main wing you really do not have an adequate picture of the global lift regime. I also feel the present crop of dumbed-down retrofit AoA gauges without number scale are the right approach. It's too much like an idiot light in a passenger car, just another black box warning to disregard. A fairly accurate number band with color designations is the best presentation in my view, and it can be digitally enhanced to include attitude corrections the same way virtual attitude indicators shout messages to the pilot in unusual attitude scenarios. I would not argue for mandated inclusion in existing aircraft due to expense mostly, but you have to start somewhere.