I have one propellor managed system where the home directory is NFS mounted, with root_squash enabled. This means that Ssh.authorizedKey fails with permission problems. On the other hand, root can su to the user in question. It seems like it might be possible for propellor (maybe even desirable?) to write files as the owner, rather than using chown.
If propellor could fork and then setuid, that would allow this. But..
The other way would be to re-exec propellor as the user with a parameter that somehow tells it what action to run. But I don't know a general way to do that, without some way to name the property. (A problem which has also complicated some other parts of propellor eg running inside chroots.)