I always wonder who/what checks if CAs respect CAA. I know some browsers now check the certificate transparency log, but are there any that check the CAA record against the issuer of the certificate?
Even if the semantics of CAA were changed, the challenges described in paragraph 3 of this post would apply: https://www.imperialviolet.org/2015/01/17/notdane.html
could we change this? Ie. if the CAA record disappears, it would be a reason to revoke a certificate?
Then 3rd parties could scan transparency logs and CAA records and flag discrepancies.
Personally I think this is another good argument for short lived certificates and reducing reliance on revocation systems.