Party:
/party request \ - request to be in your friend's party
/party merge \ - player is the other party leader, combines the parties into one
/party kick toggle \ - prevents you from being kicked from your server (defaults to you will be kicked), used for example in bed wars games where you don't want to be kicked

Creative:
Regular players can merge plots
/plot coop - player can build while owner is OFFLINE
Players cannot spam/post NSFW (chat filters)

Bedwars:
Also chat filters
Better anti-cheat maybe? I get that it's really difficult, and the current anti-cheat is already really good
Cosmetics for ranked players

Duels:
Better anti-cheat maybe? I know it might be already in the works

Lobby:
Cosmetics for ranked players

yes