Certificate for a third-party web host using CSR

[rg305]

@jared.m

Yes, it’s possible. However, not ideal, as you’ll need to undergo a manual procedure every couple months to renew the certificate as they only last 90 days.
...
However, in order to do so, you would either need to control the domain’s DNS records,

@alexmoen

We also host the DNS service for the entire domain

A "manual" process at each renewal (60-90 days).
You would need to charge for your time.
Or somehow develop software to automatically accommodate this single clients needs.
[not worth the effort - IMHO]