Have (Auto) Tags for Extensions.
Extensions on Twitch are part of the entire streaming experience.
Some people like putting some sounds and blerps, some others have detailed overlays of their decks, and some are outright full fledged games. There is a couple extensions changing games entirely as well, letting you interact with the games themselves.
... however, there is no way currently to search for people using those. Trying to do so leads you to either the channels of those very same extensions, or to... weird accounts, but no channel using those will ever appear on the page.
Having tags for extensions would change this and help communities using them discover each other, and grow altogether.
A bonus feature would be to enable/disable the extension auto-tagging itself, so that whenever you're not using it on this particular stream, the viewer doesn't get bamboozled.