I've overlooked the whole 'Expansion Workshop' too and found out some interesting ideas. Maybe we can try one of them for collaborative exp.
I've 'uped' the threads:
- The Relics - there is an idea of bonus tiles (like in H&G)
- The Ruins - the idea is not so clear, but graphics is good and may inspire for smth else
- Reconstruction - the idea is close to Bridges, but for city building
- Sorcerers - don't know where the title came from, but the main idea is removal of already placed tiles (or maybe deactivation)
Bonus tiles sound good to me.