Hi! I feel like a really neat feature that could be added to OGS without too much effort (hopefully!) would be a SGF library viewer where moderators could add well known games that are available publicly for free like old go masters games or some tournament games.
An extra mile feature would be to have commentary channels that could be selected when watching the game and people can submit their commentaries for that game (and even better would be a voting for the commentaries).
I don’t know if this was suggested or not, but it would be an invaluable study tool!