On all of the above, we're in total agreement.
MCAS did not have the redundancy of reading/comparing data from both AoA sensors.

But your original post stated "Redundancy was made an optional extra..." and went on to describe the 2 pilot display options. This suggests that buying these options would've provided redundancy and avoided the crashes.
However :

• the plane has 2 AoA sensors (options purchased or not)
• MCAS only reads from one of these sensors (options purchased or not). Only reading from one indicator, despite 2 being onboard, is a major factor in these crashes.

Option #1 - AoA indication to the pilots
AoA really only means something to the pilot if the angle is too high, they would be approaching an aerodynamic stall ... the airflow over the wings is disrupted to the point of a serious loss of lift.
Basic Airmanship : pilots should be able to note they're approaching a stall situation based on pitch (determined by the Attitude Indicator you mentioned), airspeed, control effectiveness and the stall warning.
Aircraft don't typically have an AoA indicator. The pilot should know aerodynamics and have the stall warning as a backup.

Option #2 - AoA Disagree Warning (the 2 AoA sensors disagree with each other beyond some prescribed/acceptable variance).
I assume the AoA sensors are on the plane to support the stall warning system (and possibly the autopilot).
Despite the faulty AoA issuing a false "nose too high" indication, the stall warning did not activate on either crash (nor the Lion Air crash on the same plane on its previous flight).
Therefore: I assume the stall warning system had some redundancy programmed in. The "other" AoA sensor did not sense "nose high" and based on pitch & airspeed, the "other" AoA's data seemed more logical than the "nose high" data. No stall warning issued.
MCAS read the faulty AoA sensor, thought the nose was too high, thus issued continuous nose down trim inputs.
An "AoA Disagree" light would've only helped if the pilots knew all of the below :

• what an "MCAS" was
• MCAS only reads from a single AoA sensor
• if the 2 AoA sensors disagree, and if the sensor read by MCAS is the incorrect reading, and if that false reading is "too high" then MCAS is going to go crazy

The Lion Air pilots had no knowledge of any of those bullet points.
The Ethiopian pilots should've had knowledge of MCAS, but to what extent I have no idea. It's possible that with an AoA Disagree light they may have recognized that their "control problems" were "that MCAS thing" a little sooner and deactivated the trim switches earlier.
The Indonesian report of the Lion Air crash is out. It lists many factors as contributing to the crash. In my quick scan, it does not list the lack of purchasing the AoA options as a factor.
Your post has lead at least one FTer (ryan182) to believe that the lack of this $55,000 option(s) is what brought the planes down. Not true.

I hope I'm not sounding as if I'm arguing with you. You're one of my favorite and most respected posters here. This is just "casual debate"
I think we're way more in agreement, with the problem word being "redundancy". Yea, buying the option(s) provides redundancy; but the planes crashed because MCAS lacks the redundancy of reading/comparing/validating data from both AoA sensors.
Oh ... your post that I originally replied to have been moved to the "other thread", but followups to it haven't