Malte,
I would think the content of a notification would depend on the content type, so a general content repository implementation wouldn't really work.
Besides this, I think the notification stuff is implemented backwards. Right now the notification text is rendered when an object is created or updated. I think the search model, where an entry is made into the search queue, and the search data is entered into the index in a scheduled procedure, is better.
This way rendering of the notificaitont text can occur in the background.
