Although it's not clear that we'll ever put other types of objects on workboards, it seems generally bad that you need to modify ManiphestTask to get a new ordering.
Pull the ordering logic out into a ProjectColumnOrder hierarchy instead, and let each ordering define the things it needs to work (name, icon, what headers look like, how different objects are sorted, and how to apply an edit when you drop an object under a header).
Then move the existing "Natural" and "Priority" orders into this new hierarchy.
This has a minor bug where using the "Edit" workflow to change a card's priority on a priority-ordered board doesn't fully refresh card/header order since the response isn't ordering-aware. I'll fix that in an upcoming change.