That one is easy: Just throw it away completely. Systemd is a major redesign of a major, critical Linux component.You would think that there is a very good, solid, compelling reason to do so. Apparently all they really have is "it boots faster". (And apparently id does not even do that in quite a few circumstances...)
My personal theory is that the NSA planned systemd as a project to sabotage Linux security (remember that Red Hat is primarily funded by the US military): Put an incompetent team with big egos in charge (Poettering and Sivers are certainly that), give them delusions of grandeur, make sure the BSD people ignore it by explicitly denying portability, and then just wait while the cretins produce a bloated, easy-to-exploit mess. (This "init-system" includes a freaking web-server! How stupid can you get?)
No need to place any backdoors, and all the countless vulnerabilities are genuine mistakes! Genius!