This has already been possible, the patch modifying run.c
to be able to do this is not even 400 lines long and was mostly just exposing its feature in a different way. (the entire patch was <1.5k lines, with most being docs, tests and a bit of plumbing for the colored terminal)
Basically.
systemd-run
was already able to do it, all that really changed is the interface for it. The change torun.c
in the patch itself was <400LOC, and the entire patch was <1.4k lines with most being docs, tests and utils for coloring the terminal.