Hmm, I thought about your suggestion for a while, but I have the feeling that this is not the right place to start/stop syncthing-inotify.
If it really should be started together with syncthing and also stoppped together with syncthing every time, then one could establish this dependency
- either in the syncthing binary itself
- or in the corresponding systemd unit files.
Probably you know more about whether this is appropriate for the systemd unit files, as you have written most of them, IIRC.