Having a CAA record and pointing to a CA like Let's Encrypt that uses domain validation from multiple vantage points on the Internet is a useful idea and raises the bar for an adversary.
I should point out that BGP attacks can also target the CAA records themselves since the DNS ecosystem is itself insecure. This is why such attacks are not easy to defend against, and require holistic improvements across internet routing, PKI, and web security practices.....
Indeed, a number of internet services and applications are vulnerable to BGP hijacking and interception attacks, including TLS/digital certificates, anonymity systems such as Tor, and cryptocurrencies such as Bitcoin.
For readers interested in understanding the technical details about potential BGP attacks on domain validation, which serve as a motivation for Let's Encrypt's multi-perspective validation deployment, see the following paper from USENIX Security: https://www.usenix.org/conference/usenixsecurity18/presentat...
If the domain is hosted on a /24, then more specific routes will be filtered out by default in most ASes. Also, with the increasing adoption of RPKI, in conjunction with its maxlength option, more specific attacks will be a challenge for adversaries.
I should point out that BGP attacks can also target the CAA records themselves since the DNS ecosystem is itself insecure. This is why such attacks are not easy to defend against, and require holistic improvements across internet routing, PKI, and web security practices.....