I feel that a few of features that are new, or in testing, on Twitch had a dedicated place on the page to run instead obstructing streams , or flashing up in chat.

Having a small area (maybe the top 1/4 of the chat area on desktop) to host these features wouldn't be that intrusive, and could be used as a place to display small ads for non-subs, and maybe the area could be used for the streamer to host custom apps (like overlays) for subscribers.

I'm a huge fan of consistency, so having an area like that to test new features without disrupting the viewing experience (even if it does show ads most of the time) is a huge.