Im planning at least to provide more documentation, when I learn guix and dmd more.
I'm a huge fan of Lisp-based languages, but this thing actually wants people to use Lisp for creating service files!
http://www.gnu.org/software/dmd/manual/dmd.html#Service-Exam...
Not even data-based lisp like Clojure's data format (the one that Light Table uses for its configs, forget the name), but full-on lisp!. That would be a maintenance nightmare for sys admins.
Not to mention that it seems rather sparse in basic features... I couldn't find any example in the manual for setting users & groups or permissions. These are fundamental.
I love the fact that the configuration is written in Guile. Data is code and code is data after all. I think you're exaggerating the maintenance nightmare. In fact, the Guix project has already proven that newcomers who don't really know s-expression style syntax can write software packages.
The only way to actually manage such a DSL/Schema is to provide a way to "break out" of it into a general purpose language - that's what systemd does by allowing you to run shell scripts in the case you're not using a "standard" service, and it's also what the Nix expression language does in order to build software.
It's far easier to just provide a fully capable language up front - and abstract the common patterns into functions or macros to simplify the usage for users. sysv has worked well with just shell scripts for years, despite it being a sub-standard general purpose language - although various hacks like the LSB init headers have been added to provide some kind of structure to them - a problem that will be better solved with records in Guile.
As for maintenance, I see it as a big plus - with a language like Guile you have access to a useful REPL and debugger - no need to roll your own debugging interface or inspect log files. On top of that, having a dynamic language makes it easier to develop and test patches for new requirements - you're not forced to recompile and restart your DSL.