It would be really nice if Airbnb allowed this. I have a guest who I've already hosted twice who has been a major pain.
On her second stay she changed the date, then after changing the date asked if I could cancel because it was supposed to rain, but then decided to come anyway.
She instant booked for a third stay, then a week later asked to alter THOSE dates. Then after the alteration she asked to change the date AGAIN because she forgot about something else she had going on. At this point I was done dealing with her so I blocked all upcoming weekends and told her I didn't have anything else available but she could cancel for a full refund. She canceled.
But she can instant book again in the future and I'd really love to not have to deal with her again.