Yes it is possible in theory to modify an existing agent to use an API from the metadata provider, and once the agent is configured on the server, the movie rating would show on ANY client…
I would have thought the movie rating that is shown on the dvd and bluray and decided in the US by the MPAA (http://www.mpaa.org/film-ratings/) would be definitive. So you trust that very rating coming from IMDB for all movies, despite there being only one association giving the movie ratings, therefore, it should be identical in any database, for the same region (since other regions do use other rating systems).
Can you tell use why the movie rating you see on the agent you didn’t name is “not very definitive” ?
Can you prove or have any indication it is “very definitive” on IMDB ?
There is no official IMDb agent for Plex (because IMDb doesn’t provide a free/open API and doesn’t want their data to be used for scraping), but there is however an unofficial agent: http://forums.plexapp.com/index.php/topic/21894-unofficial-imdb-api/
