Do you have to write and maintain your own init scripts, or is that created during installation?
Packages should come with the necessary scripts (on Gentoo and Alpine they do), but if they don't for some reason then writing them is pretty simple. I think the updated layout really only needs dependencies and a couple variables defined.
Void uses Runit which is even simpler, you have one directory per service and at least a script called "run" in there which gets executed by the supervisor. The is usually just one line, that's all it takes to make a service work. It also has the supervisor take care of handling logging, similar to what Systemd does. I think it's a very clean, modern take on classic init, except that dependency/ordering doesn't exist - it just retries until things fall into place. Works well though.