Making a program to change a users realm list would be easy as hell... a simple File write or just simply replace the file with an embedded one... Then depending on where your hosting your DB for private server... You can just look at your access logs to see who has tryed to log in (mine shows the Acct//pass that tryed to login) ... really its much easier and less complicated then your making it out to be. Good luck buddy.
wanna get complicated? learn OpenGL xD ..
But seriously, have fun coding

Thats the whole point remember