If the AOA sensor is safety critical they need three, rather than two.

The inherent problem with two is if one is feeding false data, you don't know which one, whereas if you have three (or more; but an odd number) you can cross-check the data and drop the faulty one.

It is a very common strategy already for commercial aviation and is called "voting logic."

> A more reliable form of voting logic involves an odd number of three devices or more. All perform identical functions and the outputs are compared by the voting logic. The voting logic establishes a majority when there is a disagreement, and the majority will act to deactivate the output from other device(s) that disagree. A single fault will not interrupt normal operation. This technique is used with avionics systems, such as those responsible for operation of the Space Shuttle.

But the real crux here is: Is the AOA sensor safety critical or not? If it can fail-safe then they can likely continue as it is currently designed. But if its failure state can cause an aircraft crash, then it becomes a safety critical component.