Hi Paul,
I have seen this question, or versions of it several times. Currently it is not possible. I agree though, that it is a great idea, and should be. I would encourage you to post this idea in the "host voice" section of the community. This is not a discussion between hosts, but a forum for hosts to post ideas directly to the company. If enough people comment or "like" the idea, then Airbnb will review it. No guarantees, but they have inplemented host suggested ideas in the past..
Better yet, do a search for someone else's suggestion (there are several) and then comment or "thumbs up" it. A review by the company depends on how many people respond to a comment.
Good luck!