Changing FCKeditor defaults for existing mediawiki users

I'm currently running Mediawiki 1.13 and the FCK editor works great!
I'm able to default all the FCK configuration settings for new users as well as anonymous users. However what I would like to do ensure that the editor is disabled for existing users. If the user exists within Mediawiki the editor defaults to on. With over 1K users on my wiki I would like the editor to default to "off" until they wish to try it out.

Any help would be appreciated.

Thanks