Thank you for your replies and let me apologize for not being more specific in my original post.
I know that regular addons aren't loaded until you enter the world and that the data to fill out the character list is sent from the server. However, from what I can see in the Interface.mpq/GlueXML/CharacterSelect.lua file it's a very simple loop that lists the chars on my screen. Wouldn't it be possible to like.. store these results in a list of some sort, add another loop or whatever to sort the chars and then put this .lua file in the "WoW/interface/GlueXML/"-folder? =)
Thanks in advance for any tip! =)
edit: doesn't seem like the game wants me to have files in that folder (appends a .old to it) so I guess this won't work :'(