It could be very helpful to allow users to add custom columns to tables based on the column configuration page and related fields. This could be used for adding specific fields to hold queue etc, item search, holdings table. I think we'd probably want to list which database tables were easily available for each interface table, ie holds queue should have borrowers, items, biblios, reserves.
Alternatively, just add all the possible options (like all the holds info to holds tables) and by default turn them off so they can be turned on easily.