Yeah i think this is a good idea it would make Clan Wars a bit easier to setup, and for what SmallBowl said i agree with because not very many people war with prizes and if they wanna they would still have that option just not as convenient as this.
I think for the people that can setup wars on the clan being invited should get small popups or something idk i feel like a little whisper bar that says they have been invited or challanged or whatever could be kinda cool