So I came up with the idea of a public playlist when I was trying to figure out how my friends and I can share a playlist. I soon realized that this isn't an option for playlists, and I believe it is a good idea. Here's how it would work.
1 person would be the host, and he/she/they could invite up to 10 people to collab. (Unlimited if they have premium.) If the people accept, they could edit and add songs, but the playlist would only show up on the host's profile. Next to the song, it would show who added that song and when.
Hopefully, you guys vote for my idea!