meleagertoo,
First you should confirm if the Boeing option for three AoA applies to the 737. I suspect not, because as you argue this would have been the simpler option.
Second, the modifications to the Max appear contain the adverse effects of AoA and MCAS with computation using the existing two AoA sensors, thus changing to three would be a big issue particularly if not required for return to service.
EASA's position has to be confirmed; their preference was for three. We wait with interest if the proposals based on two are sufficient or not. I suspect that they will be because the MCAS argument is about the required level of safety for an existing certification. However, future certifications - MAX 10 perhaps might be argued as requiring safety improvements re multiple failures, alerting, workload, confusion, etc.