This feature would be amazing, and it would put more purpose into clans.
What is it?
Clan bonuses would be for the whole clan when a certain amount of gold has been deposited in the clan by its members. Of course the rewards would not be too easily achieved because they affect everyone in the clan.
Currently, clans are not too useful as all they are used for is troop donations, and communication.
Types of bonuses
Bonuses that the clan would work towards could be split up into branches, allowing for more diverse clans.
For example, if there were 3 branches, some people might prefer one branch over the other for their certain play style, so they'd find a clan thats progressing in the branch they want.
3 possible branches could be Defense, Offense, and Loot.
The offense branch could include upgrades for troops hit points, damage, speed etc. The defense branch could improve the defenses hit points and damage, rate of fire etc. The loot branch could have upgrades for mine/collectors production, much bigger loot bonuses, further upgrade for storages, lower troop cost etc.
Here is a link for an example of what it could look like:
In this image, each upgrade could can upgraded 5 times, with each upgrade doing 2%, with exceptions for some upgrades. Level 1 would cost 1,500,000 gold, Level 2 would cost 3 million, Level 3 for 6 million, Level 4 for 12 million, and Level 5 for 24 million.
How could it happen?
To add this feature in, there could be a seperate section between the tabs "My Clan" and "Search Clans" shown in the picture below. This section would include the different branches.