I'm doing a project for a client at the moment that requires feed-specific logic for things like data-sanitisation and enrichment before saving a post. I rewrote the post-by-feed package to instantiate a FeedHandler object from a factory method based on a new attribute on the feed document. The original feed handler will be available in as the DefaultFeedHandler.
Is there broader interest in this logic for Telescope? I'm happy to create a pull request for this.