EDIT: I cut this thread down per the general recommendation in the sticky to be more concise. I’ll repost the other ideas I had here in separate threads another time.
One way to require the use more of the game’s features would be to have a steeper progression path on higher difficulties. For example, housing currently requires one of 2 particular goods to upgrade each tier. Higher difficulties could require both goods to be supplied, or even three or more, which could provide a scalable use case for new goods types. This could apply to food as well, where more types of food would be required for housing to upgrade. Currently there is only one “luxury food” item; these changes to difficulty options would provide a use case for additional luxury foods without necessarily having to add new housing tiers.