We have been doing this since quite a while, so that in v256 22 of our dependencies have been reworked like that.
This has the benefit that on a typical system the systemd binary itself only pulls in the C library (including libm), libmount, libselinux, libaudit and libseccomp.
Net result: we have a tiny required dependency footprint, but can still provide a large feature set, if the optional deps happen to be installed.