I would like to create a customfield type which is a tag input, and each instance of that customfield would be configured to point to a specific 'Tag collection'.

So the current state the user profile has a hard coded tag area of

• 'User interests' which might point at the 'Default collection'

Instead I would like to be able to configure for example 3 different fields:

• 'Sport interests' points to the 'Sport collection'
• 'Professional interests' points to the 'Professional collection'
• 'Favorite dog breed' points to the 'Animal breeds collection'

So each instance of the customfield would define it's own tagarea, and there could be instances of these fields in the user profile, or in any other place where those fields can be added.

The db/tag.php file is static quite limited, what I'm proposing is a hook / callback where a plugin returns a dynamic list of 'tag area' objects. Each object has methods to directly handle things, so the 'callback' and 'callbackfile' are not needed, 'component' is implicit in the object namespace etc