I was thinking there should be a sort of rating system for players in clan that can be seen by other players within that clan that shows clanmates how effective someone is in clan wars.
Average number of stars per war
Wars participated in
Some way of showing how often/how much higher than the recommended target is attacked
Now, the above recommended target one is the most important. If someone is constantly attacking above their recommended and getting stars, they're going to be valuable to the clan. This also prevents people from attacking lower than recommended just to get a higher ranking; you don't have half the clan attacking the same people.
However, the top 10-20% of the clan would be exempt from the recommended target. This would be because if your recommended target is #30 but you attack #20 and get 2 stars, that's a good boost to your rating. But being a top 5 player in your clan, your recommended target might be the other clans #1 and someone already got 3 stars on them, which leaves you having to attack below the recommended and thus, getting a lower rating. Since top clan players don't have recommended target stats counted, they should have participation matter more.
This entire thing would help out the clan leaders know who's helping the clan and who's hurting it. They'd be able to more accurately see who is purposely attacking lower rated bases just to get war win loot, or to make it seem like they're fully participating.
On top of that, the top, say, 3 players (based on their effectiveness rating) of the season could get either gems, or a resource boost, or something as prize for helping their clan more so than the others.
I came up with this yesterday and at the time there was other stats that I wanted to take into account for the rating but I forgot what they were. If I remember I'll add them in.