I found this: https://github.com/woju/systemd-dehydrated/

It essentially creates per-domain units. However, those are timers, not services, because the underlying tool doesn't have long-running daemon, it's designed to run off cron. So I can't depend on them directly, and I also need to add multitude of dropins that will restart or reload services that use certificates (https://github.com/woju/systemd-dehydrated/blob/master/contr...). Coudn't figure out any way that would automate this better.

Well, every timer needs a service to activate. And at a cursory glance, this project has oneshot services, which is what I would expect for something like this. So your units (e.g. a webserver) would take After= and Wants=/Requires= on the given oneshot services.

This project looks neat! I might give it a try. I had never heard of dehydrated, but I don't particularly love certbot, and would certainly be willing to try.