Since i have been in many clan or lead some clan in the past, i have come the understanding that ally list is not mandatory for a clan to have and even if they do it, it backs to how they manage the clan and how the clan treat the ally. Some clan create an event that only their member and ally could join, or some let some of picked ally to give their opinion toward the recruitment process of that clan and so on. The benefit of ally is up to the clan management instead of the clan system, be flexible and/or innovative to it instead of forcing the ally to go to war for you. But, hey i will give you the benefit of doubt and state my honest opinion regarding this.
This idea leads me to some questions:
1. There will be no doubt that there will be a case where they just let "ally" to do wars for them without any real clan member participate the wars (warring 1 vs different member is a thing yes). Which is kinda dumb since war supposedly a group effort of that clan and ally should have not intervene with that, imo. With your idea, is there a way to prevent from this to happen?
2. Clan wars with current system gives points to your activity point and ranks. With your system, would that points are only given to the clan they are representing or it's distributed too to the ally's clan if they have any?
3. By going with your idea, there would be a new similar thing to toriclan to manage your ally list so war system could acknowledge that those individual or group are counted as an ally. From my point of view, it is meaningless to create something that is not entirely small but only has one importance.