> I can see why Poettering does not want to do 2x work
It's always a dangerous exercice to try to double-guess an author, but from reading the systemd code I get the impression that he's deliberately using non-portable features, with relish. (See for example the systematic use of the "%m" printf descriptor where strerror would do just fine. 302 occurrences.)
The other reason for non-portable code, of course, is that systemd is doing a lot of low-level system stuff that usually belongs in separate utilities. Much of that could probably be compiled out if Poettering were to accept patches that optionally disable parts of systemd functionality.