I would love for such a thing (and have thought about doing it myself). But as systemd's capabilities grow more and more expansive, and with its lack of modularity, it becomes harder and harder to write a replacement for it. Of course, even replacing only a piece of systemd's functionality (for example its process manager) would still be beneficial, but systemd would continue to be the only real choice for many.

I would suggest that simple common sense might prevent such a thing. It's not without reason that the older, wider heads always kept initd simple, in part to prevent it becoming an unnavigable monstrosity. The very idea of the "legacy" init implementations creating files, let alone suid root files, is laughable.