How about increasing the stakes?

Getting war loot is awesome, but getting more war loot is even better.

How about an "entrance fee" for every war? It will cost an xx amount of resources. These resources are put in a pot. The winners get the war loot bonus plus whatever was in the pot. I won't get into details as to how much because obviously, TH6s and under don't get DE, but the fee can be according to TH just to keep it simple. It may vary because of the difference in amount of THs

Now we can't force everyone to pay the entrance fee, so this would allow only active members to be a part of war, eliminating the opt-in/opt-out requests and the kick/invite option.

There could be other clanwar incentives like "Heroic Offense / Defense" pots where interested players can invest an equal amount of resources for themselves to win. Whoever Supercell's algorithim decides gets the awards gets the pot! So even players in losing war clan can "win" individual awards.

This would make attacking more bold and braver, and it might even ruin wars for some clans (TH7s going for TH9s with mass dragon lol). But that adds a different angle in strategy.

There shouldn't be a cover charge for clan wars. You get the win bonus or you don't. Not a terrible idea, but I don't see a need for it.