I think there should be a option for the clan leader to select the members before starting a war. The automatic selection many times leave out important players and select in players who may not contribute well to war. A option to select participating clans will increase better strategies to fight war. It may help more low level clans then high level clans but something like that should be there.
If they are important to war have them push. The method of choosing who is included is very simple. Round by 5s on the clan rank and everyone after the last 5 is out. I agree there needs to be some designation as to who wars but if someone is really important to war they should push to be included in the war. At most only the bottom 4 are out.