AOAs are nice but, based on my time as an A-10 and F-15E fighter pilot, AOA is simply not that critical of a system. Fighters fly all sorts of maneuvers at all sorts of air speeds and attitudes that are far more extreme than some straight and level commercial jet, and having lost an AOA (Bird strike low level route) you just fly the jet. You, if you are trained properly, you know the AOA without some gauge. If it looks right and feels right, then the AOA is nice but you wont lose control or fall out of the sky if you lose the gauge.