1. The solution to this is to write a translator from systemd units (those of .service type) to the desired kind of unit. I haven't looked into dmd, but this should be possible at least for the majority of units.

2. This was going to be a problem in any case i.e. had most distros switched to openRC one would still have been faced with the task of producing a suitable collection of service configuration files for dmd and then adapting them to dmd's specfic featureset.