(I actually wanted to create a feature proposal/request however JIRA did not offer me to select those)
I had several occasions where I wanted to use socket auth for different usernames:
Using authentication_string in the user table to specify the allowed system user name which may authenticate as the corresponding mysql user over socket.
I already created a patch for this in my own build, which I could contribute if described feature is wanted. Currently my authentication does the following:
Another feature idea is to allow a comma seperated list of different groups/users...
Btw just noticed that mysql supports specifying an alternative user name for the socket_auth plugin, however they accept both: