I mean like okay we have messaging with in clan members but say we wanna message someone that used to be in your clan and you wanna ask them back and they are already in another clan so you cant invite them you could message them, or say you wanna talk to your leader and only your leader about something and dont want others to see you could message just that person and we can always add a report bar for harassment!
I don't find this feature needed. I'm able to tell players who join to ethier add me on social media or download line for the clan. If I need to talk to someone out of a clan; I'd leave and go do so