I'd be far happier if we were just allowed to ignore the signs and have strict liability for the consequences if we screw up doing so. Being subject to fines and harassment by law enforcement is what I don't like.
a) That's possible depending on how you quantify ability because average is influenced by outliers.
b) Is that supposed to be a rebuttal or something? I think "do whatever but strict liability if you F up" would be fine even for average and below average drivers. That's mostly how things already work in practice.