long, summary of the idea
essentially:
There'd be an X amount of slots of personal emojis, they'd be username-prefixed, and hidden by default for other users. Each emoji uploaded or changed would have to go through a moderator queue, to obviously root out the bad ones.
This would allow personal expression, and development of (new) emojis that could then be elevated into the wider server emoji list.
These personal emojis would also be deleted/removed/made inaccessible/hidden after the user leaves the server or deletes their account, this'd be mostly to complete the lifecycle of that process, and allows lingering emojis not to pile up after many years of use.