Not every new feature has to be a protocol extension though? Some clients just lack some sugar coating client-sided features. As for protocol extensions, you could always just disable them in-client on servers that don't support said extensions if anything. But my focus is on making more cleaned up IRC clients, a lot of them feel like they're stuck in time when I know there's lots of things that could be done to them to both make them user-friendlier for newcomers and make them a little more convenient to use.