Hello.
I'm fairly sertain that this has allready been brought up considering how nice it would be.
I'm also fairly sertain it must be pretty difficult to accomplish since it hasn't been implemented as of yet.
However, I think it would be EXTREEEEEEMLY useful, if Guild and Friends list permissions were allowed to overlap. For instance, if you have the guild included, you can still add friends not in guild to a list that could have access to your lair/plot. While the guild still had access.
I just felt the need to reiterate this desire since issues come up for me on this so often.
Thank you for considering.