(Note: I’m ignoring shuffle and vote modes for simplicity, but these may need to be considered too).
If you’re watching a video from one playlist and then switch to another, the next video chosen will be the one at the top of the new playlist, which is fine behaviour.
However, sometimes I switch to another playlist only to make a quick change to it, and then I switch back to the previous playlist before the current video has ended. In this situation, I think w2g should act as if the playlist had never changed, and continue onwards to the next video, instead of jumping back to the start of the playlist.
A related issue is that when everyone disconnects, the next time we open w2g it remembers which video we were on, but not the position in the playlist, so it will also go back to the first video in the playlist once the current video has ended. So if we want to continue watching the playlist from where we left off, we have to locate the current video within the list and press that play button instead.