On the contrary I have personally seen the attacks and the impact. My understanding was that CAs are required to do that by spec and Let's Encrypt already does that.

The Use case - Lot of SAAS based products allow/require the administrators to prove the ownership of a domain via ACME methods. The administrators then are allowed to manage the profiles for users that have email address with same domains in the SAAS product.

Ironically the testing setup itself used the network hack for the successful ACME challenge