IF (of course it's still a big IF) a faulty AOA sensor input is at fault again here feeding MCAS invalid AOA position, a person might want to look into the recent Quality assurance and manufacturing of those AOA probes. I would assume the Lion Air and ET Max's are not too far off of each other, which may have a similar batch of AOA probes.
I agree that the simple and appropriate fix to the system would be to have to see 2 valid AOA inputs for a stall or near stall position. It's hard to believe they would engineer such a critical system with only one AOA input required.