You know how to create a module and that it's easier to add a autocomplete field like node reference or user reference to an existing content type with CCK.
When you have your on module you can create an autocomplete field to any field of the database
This is how to remove a CCK-field with a special condition. If you just want to hide the field in hull node and/or teaser view you can configure it at Manage fields / Display fields at your content type.
Don't forget to refresh your them registry before testing, otherwise you wont see any difference. If you are using the admin menu module ( http://drupal.org/project/admin_menu) you find it in the first menu, Flush all cashes /Theme registry.
Create a file, content-field.tpl.php, in your theme folder.
Add the following content to this file:
