[dziobak]

Just to make sure I get this right: "I'm thinking about adding functionality that will find IMDb_ID from TMDB_ID" means it will find it if it's there or does it mean that it will somehow determine which IMDB ID corresponds to the title by itself?

You have few tv series scraped by TheMovieDB add-on, right? In that case, has tvshow/episode the IMDB ID besides TMDB ID? Or, simply, does our add-on update tvshow/episode or put in update.log some info about problems?
If there is lack of IMDB ID, add-on could look for this ID based on TMDB ID (like does in current version when search IMDB ID from TVDB ID).