There could be some really off the wall stuff that could be mined to great effect in the Star Wars universe. How about that old episode zero storyline? I'd watch a young Qui-Gon movie showing how he became so independent of the Jedi Order. A full-on Shadows of the Empire movie? I could even see something like a Nien Nunb movie that makes a fun story out of how he found himself as Lando's copilot out of seemingly nowhere (something I've wondered since I was a kid.)
Beyond the obvious onslaught of Marvel movies since 09, is there any precedent for a movie series like they've proposed? I can't think of anything that comes close. Thomas the Train maybe, he has a new movie (on video anyway) every year.