May I suggest to add a tiny feature?
Currently, when port forwarding with PIA has been configured, the port is saved to port.dat. Would it be possible to add a secondary action to that: run a bash script.
Allow users to add an environment variable in Compose that specifies the path of the .sh file. This way we do not need inotify, a seperate container etc. and users can use a script for their favourite torrent client to update the port.

For QBittorrent: #3 (comment)
For Transmission: #3 (comment)
For Deluge: #16 (comment)

This github has become a nice repository of interesting info :)