This idea has been suggested many times before. A lot of the...ahem...experienced forumers just get super itchy and twitchy whenever they see an idea that has already been suggested. (Confession:I'm one of them).
In any case, as you can see in my signature, I'm publicly already campaigning for this (kinda). I agree that this should be implemented despite some of the reasons it might not be. However much I support this idea, I am a bit tired of seeing these again and again and commenting again and again, so I'm just going to copy some stuff from my thread about the exact idea
http://forum.supercell.net/showthrea...pt-In-Out-Poll
Reasons:
The main reason is because
people don't want to kick people and invite them just so they can opt outon war. While that is a solution, it has some consequences, including misunderstandings, drama (omg, you kicked me out so that I wouldn't be in war) and loss of donation statistics.
Some might argue that if one does not wish to participate in war, one must simply join a clan that does not participate in war. The reason this is not true for many people is that those who care about being able to opt out are more likely to be loyal members, or at least friends with many. Leaving as a group is not a solution either since the
group of friends would still be split between warring and not warring. Splitting the group results in the splitting of friends, which lowers the amount of motivations to keep playing CoC. If sister/feeder clans been implemented, that would be a long workwaround that could still be flawed.
There is another reason that this is suggested, which is that
players will still "have a life" outside of CoC. This includes vacations, examinations, business trips, blackouts (+and other force majuere disasters) in the residence of one player which doesn't affect the others physically etc.. Thus, some players would only opt out some times and return to war actively.
Here is a reply from Supercell in an old thread (I don't have link to)
Please note that they did not rule it out, they are keeping tabs and so we should just keep our fingers crossed and wait.