This proposal is to add support to the
Key protection: rather than deploying the actual private key associated with the certificate that was issued to you by the CA to each server that fronts TLS, one can instead create and issue a delegated credential. This credential can have a much shorter life span than that of the original certificate and one does not need to contact the CA to have it provisioned each time. The client can still verify the chain of trust as the delegated credential is still signed by the certificate obtained by the CA.
Experimentation for new PK algorithms: in addition to the security benefits it provides to protecting keys, it enables for servers to experiment rolling out support for new authentication mechanisms which are tied to the certificate being served. Essentially, the server can try out a new authentication type without altering the certificate the was issued to them by the CA.