I personally need a way to determine the game currently set for a channel even if it isn’t live, for shoutouts. That is the one thing that I still use the v5 API to get.
Being able to determine and update the game and stream title through the API would also be nice. I don’t make use of that in my own code, but one of the programs I use (Chatty) does, and that’s a handy feature to have in the middle of a stream.