Command: /main [charName] or /mainchar [charName]
Precheck: Checks to see if the character is using the same IP as the character using the command (same as /transfer), if true sets an attribute on the character to this name/number.
Usage: On login, if value is set, changes the login message.
Ratty [Ratheart] has entered the game.

Some (many) people prefer to keep some or all of their alts confidential.
I guess this would be a player option that they could choose to use or not use.

Staffers already see this when a new player starts (shows their alts).

Not difficult to do if their is a demand for it.