I had a team member explain the project vastly differently to me. Can you provide a link that LE is only for personal/casual use?
As a webhost we have offered SSL certificates to customers for ages. Unless it's free you will see very little uptake. Which eliminates the main purpose for LE to exist, from what I was told.
I also have a rather compelling use case for far more than 20 subdomain certificates a week, but there is absolutely no "market" for that use-case - it simply increases Internet security. Which was the entire stated goal of the project, I thought.
First I've heard that LE is only for personal use :)
If you have per-user sub-domains, just get a wildcard cert, pay for it, and cover all your users all at once. Why do you need want to go through LE for that purpose?
Let's Encrypt is a public service, aimed at operators of individual systems who host web content or email in a casual sense, were poorly served by the complexity of getting and maintaining a TLS cert, and who empirically were basically not doing TLS.
Your posited blog host is going to be a professional or semi-professional web admin. Just call up Comodo or whoever. There's a product for that need. Let's Encrypt is not it.
In the vernacular: cry me a river.