I'm still working out the bugs, but this is something I wanted for myself. It would let you add the playlist to your app/account, and also let you automatically play the next video.
I'm thinking of the following:
- rolling window of around 50 videos, where older videos get dropped
- a post is only added to the playlist if it has been up for 24 hours, so that spam posts can be removed by mods before getting on to the playlist