Uhm.
Implemented game by game? You serious?
Stored in a database by the developer? On which server?
You seem to talk about stuff that would be in a web game that has no need to be hosted on Itch to begin with. Itch web games are from small indie and amateur developers. They usually do not have the ressources nor the expertise to implement all these things on top of their game. And if they do, they do not need the profile info to do login stuff. Better yet, if they do it on their own, they are not limited to host on Itch.
I did not mean that the other things are requirements with that overhaul. I meant that the feature on its own is not a good idea. It does not fit with the rest of Itch's features and how privacy is handled and how players interact with each other while playing a game.