I agree, simply add speed to the above list. You can also add the baro alt comparator to the items the 737NG carries, probably for some good reason.
Now I think there seems to be a good reason to consider the need for a RA comparator.
Whatever the crew implication, it bothers me to think that possibly this simple feature would have saved many lives on that particular day. Before all this discussion I would have thought that disagreements between RA were monitored and classified as failures.
WE are humans, do I need to remind you examples that you very well know:
AA failing to retract speed brakes in Colombia during pull up
I could go on forever. I will never say never, will you?