Regarding questions as to what the crew should have done in response to the initial indications associated with the AOA malfunction......
FWIW, beginning on page 91 of the final accident report, the investigation team reports findings from several test scenarios performed in Boeing's E-Cab engineering simulator. These scenarios were conducted to better understand the malfunction, the indications presented to the flight crew, and the crew workload. This is a description of one of these scenarios:
The first case objective of the third scenario was to observe an “ideal” response to stick shaker and IAS and ALT DISAGREE messages after takeoff. Crews were instructed to maintain takeoff flap configuration (MCAS function will not engage with flaps extended), complete the Airspeed Unreliable and Altitude Disagree NNC and return for landing at Jakarta. There was no significant issue regarding the first case.
The report does not say how or by whom this "ideal response" was crafted. That is, we do not know if this was hindsight or if this would have been the "Boeing approved" solution if asked before these accidents ever happened. Nor does the report say if this is the ideal response going forward with the redesigned MCAS system.
Personal opinion..... this "ideal response" should have been made part of the original emergency AD that Boeing put out after the Lion Air accident rather than the lawyerly-type language that was used. It might have made a difference.