I’m not entirely sure in what cases you would want a playlist that you can play on repeat. In my personal experience, I rarely find myself wanting to re-watch anime within a short time of watching it the first time but I can imagine a few ‘specific’ scenarios where a playlist would be cool to have. Twist.moe already has the “next” button in the corner of the video when you reach the last 2 minutes of an episode which is plenty for me.
My wish for anime-viewing in the future would be some sort of “skip into” button, the same way Netflix has it. I typically don’t feel like watching the OP to an anime every single episode if I’m binge watching a show. I’m not sure if something like that would ever be possible tho since most episodes play the OP at different times.