To my thinking, the answer to this question lies in what problem we are trying to solve. Is it to reduce the cost of entry or to make pattern flying less intimidating to beginner pilots? I can't see gyros accomplishing that. Going to smaller planes for the first two classes would do it, as well as not allowing some of the fancier equipment like counter rotating props or super light planes. But allowing gyros effectively means requiring gyros to be competitive, increasing the complexity of the planes along with the cost.