Linux

sudo is not a fairly simple program. Last I checked, it had ~177k lines of code. It provides functionality far beyond what is needed of an average user. doas is a simpler alternative (also using SUID) at ~3k lines of code. It comes from OpenBSD. There is absolutely a problem when it comes to SUID binaries. If you can find a way to exploit the permissions given at the start of the SUID binary before user authentication occurs (since the UID is set before the binary runs), you have yourself a full privilege escalation vulnerability. systemd is very well integrated with the distros that use it, being the first process to run after the kernel is initialized. There will never be a point at which systemd is not functioning, but the rest of your system is perfectly fine. It is an absolutely necessary part of the system (assuming your distro uses it), and if it goes down, you have to restart your system. As such, I don't see any validity to the statement "you want to always work, even (especially!) when other things get borked". What exactly do you see as being an issue with run0? What specific part of its implementation do you seem to have a problem with? It's just a symlink to systemd-run, which is already very well tested and has been around for a long time. It's also far simpler than sudo, and removes the attack surface of running an SUID binary of its size. What "points of failure" do you see here, exactly?