Passport to join known clan
Example: I am in my clan, but has no one online and I want troop or spell to attack in the war or multiplayer attack, so I leave my clan because I found one player in the global conversation to donate that I want.
In this occasion, if I leave the clan, I need to wait the members to accept me back to the clan. But, if I have the passport for any time join the clan if it is closed or requesting invite, I don't need to wait the members accept me back.
The idea is, if the leader of the clan give me this "passport", I can join the clan how many times I need and doesn't matter if the clan is closed or with high trophies than I have. I think that there are so many players thinking about something like this.