The new, modern, cheap solid state IRS's that come in modern smart phones are not required. Modern jets have 3 or more "Real", no $%#@t certified 3 axis accelerometers and gyroscopes called IRS's or IRU's. On a Scarebus, if you call up the "bird", you have instantaneous AOA info. The pitch difference between your "bird" and you pitch bars is - tada - your AOA. A HUD would be nice, but you have the same exact display on your PFD. On a HUD it is just overlaid on the outside world. Awesome for TO and landing, but at 35K feet the PFD works just as well.
The pilots had everything they needed, including the procedures in FCOM. Most "unreliable speed" crashes have happened on TO. It is VERY diffucult to diagnose in that case. Is it unreliable speed? Windshear? At 35K, level flight, autopilot and autothrust on it is not that difficult, and a trained event on all A320 and above airbus aircraft.
Pilot error and systemic pilot training error. This should not have happened.