It would be nice, and it is sent in ClientSettingsC2SPacket. It is not really saved anywhere, but the packet is passed to the ServerPlayerEntity in setClientSettings.

I'm a total noob in Mixin, so I'll probably not try to implement this at least Soon™.

Good idea

... but
some players may want to remain anonymous. That's why there is 'ping' for players, but not 'ip'. Language stays in the gray zone between these two.
Something to consider. I am fine one way or the other.

thoughts?
I am on the fence of the language thingy, but on the 'its fine' side.

Then would you mind me working on this? Im curious to learn more about packets, so I would be interested to do this one if u don't mind...