Linked channel subs
A channel should be able to nominate linked channels that get subscriber benefits in their channel. A viewer can sub to either channel or both, maybe it shows the sub badge from the linked channel if they arent subbed to the current one, maybe there is an optional badge for people who are subbed to both.
Lets say two people regularly stream together, you as a viewer are a fan of Streamer A but they rarely stream on their own channel and instead are always on the channel of Streamer B, this would mean you could support A while watching them on B. If streamer B selects an option perhaps the sub button could ask which streamer they want to sub to, with an option for both.
The obvious example is couples but this could be used for org channels too. So if an org does an event with a bunch of their streamers tagged, subscribing could offer a choice of which streamer the sub would be too.