Ability to sell defenses and/or decorations. You can add this for any building except for Pirate Hall, Tavern, Guild Hall, Ship.
Why? Now decorations I do get, but they are already on the masterlist. But why would you want to sell defenses?
A. It was in Clash is the worst possible excuse, I'm sorry to say it like this. But we here try to keep thing refreshing and creative, not just another clash rip-off B. Even Clash players didn't understand. The only times this feature would be used is when friends/kids get a hold on your device and sell stuff "for fun".
Everybody who quits could sell their mines and distilleries, which would decimate the economy. File this under "terrible idea". Zero upside, major downside.