Just a heads up that we have written a plugin for Let's Encrypt for use by cPanel end users (https://letsencrypt-for-cpanel.com/).
Looking forward to see what the Dreamhost offering is - most control panels should have fairly simple integrations, having implemented this now.
The only complication seems to be sites that inadvertently block off access to the ".well-known" URL path, mostly through rewrite rules (blocking dotfiles such as .git). But, I think that over time, improved plugin UX can help the user deal with this problem in a pain-free way.
@arek the DNAT idea, I would dread having to deploy that, haha!