Clan hopper revenge option or new member waiting period
So I read the stickies and didn't see anything similar. How about an option to perform a revenge style attack on members who leave clans. Perhaps only available for 24hours, and only able to be performed once, by a clan elder. Another option would be to have an approx 30-60min wait period after joining a clan to be able to request troops.
Either option would discourage the common practice of players joining, requesting, and immediately leaving.