1. Allowing clans to make alliances when a clan makes an alliance they can’t be attacked 2. Trading between the clans who have joined the alliance they have with another clan 3. Resources bank somewhere you can put resources to help you to stop them being lost 4. A headquarters building which is where the clan bank would be however the headquarters can be attacked and it’s up to the clans and alliances to defend the hq 5.add a friend feature
I like #4. Require it to have rallies on it at all times to protect it and allow people to attack it like they would a player. However, I could see it needing a deposit/withdrawal log.
Would would be part of the bank and if you needed a withdrawal you can only take what you put in but you can have clan members or an alliance if you needed more