Our clan is a small one with many casual players. It causes us always problem that the half of them don't want to take part in a clan war, or they want, but they don't have time to attack for several reasons, or they don't want to spend their resources for attacking because they are collecting them for an upgrade, or so.
My idea is to have a button or something like that next to his/her name on the clan view list, where the clan member can choose weather he/she wants to join the next clan war or not. When we have enough memeber to start a clan war, then we could begin to look for an opponent clan.
There are many other clans where the members are more active and we always loose against them just because our team mates can't/don't want to attack.

I hope that not we are the only clan where these things happen, and the other ones will find this feature also usefull!