If you have XRecord, you can use the built in Transcode function.

GBPVR also has a transcode feature, but I think XRecord might be your best bet for on the fly type transcoding.

I really only ever us GBPVR on a PC as I don't have a MVP. You might want to post a question in the MVP forum asking how to transcode QuickTime so that the MVP can play them.

The Movie Trailers is really not a plugin per say, but a utility that is run to download movie trailers. Now integration in with the Theater plugin would be nice (i.e. get a listing of movies showing, and if the trailer has already been downloaded give an option to play it.).