[lmz]

Multiple keys and certs for the same hostname? Will the CA even issue that?

[cpach]

I guess it depends on the CA, but some do. Let’s Encrypt does, for example. I guess it’s useful for HA deployments, where load balancers might be spread out across multiple datacenters and stuff like that.

NB that rate limits apply https://letsencrypt.org/docs/rate-limits/