I've decided to share the "secret" of how to get the English font to look like the one of the Korean client.^
NOTE: It does just change the fonts of your UI and dialogs and chat. It doesn't affect the combat fonts of "Crit/Parry/Block/Resist etc."
All you have to do is going to your aion directory "NCSoft\Aion\L10N\ENU\data" and create there a folder called "fonts".
Now download this file -> https://www.mediafire.com/?ur0qrma67k7ymsy and place it into the new created fonts folder.
Now start your client.

This method works also with the Taiwanese, Chinese or Japanese client, however our client just holds the korean fonts in it's Data folder so you don't really need to download my file if you know where it's located. So you'd have to get it from the other client and copy it into your own client in case you wanted the TW,CH or JP font.
Regards,
Dei