Clan Resource Banks

A clan resource bank would be a virtual bank dedicated to each clan. All members of a clan could donate to that bank, and players could see how much they've contributed to it weekly. This could help determine elder, and achievements could be integrated with this.

Nobody has the option to take resources out of the bank without need for those resources (must have an upgrade that needs to be completed). Supercell would designate how many resources could be taken out of the clan bank by a series of calculations involving trophy league, amount of donations in clan, elder, and total number of clan members. Not even the leader has 100% full access to the bank, to prevent scams.

New members to the clan do not have the feature of withdrawing, but have the feature of donating.

There is a bank capacity, that can be upgraded depending on how many resources the bank holds. (Or depending on the total level of clan castles of all members). The clan must work together in order to upgrade the capacity.

You have access to all of these features through a button on the clan castle.

All resources are able to be donated.

Supercell could profit off of this idea, because: in order to have a clan bank, your clan would first have to put forth a set amount of gems to obtain it, again, the concept of working together as one.

Keep in mind that if Clash of Clans doesn't even want to think about creating a stable economy, which is what their players want, this is the closest they could get to satisfying their players, while keeping the "economy" aspect out of things.