I have no idea how well it works, what limitations it has, or how OSMC updates might affect it, but apparently it’s possible to run a Plex server on your current install. The advantage going the plex route is that it takes care of permissions, shares, firewalls, and provides for easy clients. The downside would be that everything it does is going to be independent of Kodi so any resources used by one program is going to affect the other and it’s not like there is a lot to start with on a Raspberry Pi.