A typhoon was just the first natural disaster I could think of.. A more reasonable one would be a blackout. It's not life-threatening, but they wouldn't be able to play. To come back onto CoC after and see that they were kicked out for war is just insulting to me.
The most common and accepted suggestion for war opt in/out right now is to use the war shield (or new button) in clan info to toggle yourself in or out. The leader (and possibly co) can override this. That's why I'd don't think a limit would work because if each individual player is opting in and out (because they should have the right to), then it wouldn't really work. There is already a hard limit on how many people can opt out because if the number of people opting in is less than 10, clan can't war.
A more feasible way to implement a limit (though I don't find it favorable personally), is as you suggested for the limit to be on leader override. Thus, the most a leader can override is 6(maybe), but if the entire clan individually decides to, they entire clan might be optin out.
As rwelshjr said the opted in number would be used for technical purposes.
Btw, a lot of people voluntarily just join clan (not talking about hoppers) for good donations with little regards to war. I know one other forumers who has stopped war in her clan until this feature is implemented (or "this problem is fixed" as she said it)





