Too often folks rush to upgrades and then are able to corner a market and stop purchasing more items, especially Tier 2 and 3 building materials. I suggest we remove the upgrade system from making production more efficient and instead have upgrades pertain only to speed. What would make work more efficient would be the tier of the room the production table is in. For example a Glassworks would still need their tier minimum to produce glass, but advanced upgrades won't make them more efficient, a nicer room would! This would encourage more building and more trade further into the game rather than small bottle necks of upgrades necessary to progress. Then we can combine the upgrade system with the room tier system - you max out when you have a good room AND get the upgrades, not just rushing to an upgrade and calling it done for the rest of the game.

To build on this idea, we should integrate more support options to room tiers, especially Industrial ones. These could be items made by other works that find a lull between their labors, to encourage a more diverse set of specialties as well as a more unique recipe pool that are useful. Think the same way Decorative or Carpet or Bed are categories in their respective rooms: just make more of them, make them made by diverse specialties, and have impacts for the rooms the industrial products are in.

I think these changes will make the game more exciting and interactive and more varied rather than folks making a lot of tier 2 and 3 items that go unused because they aren't "needed" for an extra star. Make buildings do more than just give XP!