How about adding a feature where an alliance can raid another alliance in between wars? This would be fun as I’d love to raid former alliance members new alliances…sort of a grudge match sort of thing. It can be done for “alliance cups” or some other type of trophy and can be done in a war style format except perhaps there’s no matchmaking period and existing defense teams are used. Attacking alliance members only get 1 flag and you can earn points towards an alliance raid wanted chest.
If it is not a full Alliance War (everyone agains everyone) then it looks like an individual raid (one to one). What is the difference?
It’s different. With alliance war, you can’t choose or reroll your opponent. With the concept I’m proposing, an alliance leader or co-leader would be able to take an alliance on a raid of another alliance without a need for the long matchmaking period or the long war preparation period. Alliance defense teams would be used to defend against attackers and the raiding allaiance teams can attack with 1 flag each. It’s a faster version of war but alliance based.
Also, I’m proposing that you can raid a specific alliance…ie if you have alliance members who leave to start another alliance, you can attack their alliance or they can attack their old alliance.
I doubt this would work because of a different strength of alliances. In AW and raids you are limited to choosing foes of a similar strength. There were lots of complaints about an unfair war matchmaking, when one alliance overpowered another one. Choosing an arbitrary alliance will result in the same disproportion: strong alliances will attack much weaker alliances for fun or for loot. On the other side, if the restrictions will be applied like in AW we’ll get another AW. 
You could create a rule where you cannot attack in alliance that is X points less then your alliance. However, it would be nice to be able to attack stronger alliances. I’m sure there would be many people that would be dying to take a crack at the top 100 alliances.