Is there an equivalent chainloader ("envfile"-style) that can be plugged into the instanced user service directories' command line? Having the same configuration file be read by tools with different behaviors (for instance, it appears the pam_env's quoting support is far more limited than envfile's) may not lead to the same results.
I wanted envfile to be compatible with intuitive and expected behaviour. If you write your files conservatively wrt what other tools accept, you should be able to read them with envfile. -- Laurent