Can systemd be used as an inetd/xinetd replacement without being an init?

Can systemd be configured (in runtime or compile time) to serve as a simple process supervisor, not as /sbin/init? If yes, are there tutorials and other documentation to follow to make customized non-init-systemd setups? If no, what other thing should be used for UNIX-socket-activated services apart from plain openbsd-inetd (which, for example, cannot chown/chmod the sockets)?