I wish I could help you, but I know very little about python. I tried learning a while ago, but was quickly distracted by something else, and my reason for needing to learn disappeared anyway. I tried looking through the quicktimebrowser script to see if I might be able to copy and paste some stuff and add a few things to make it work, but I was completely confused looking through that thing. If you figure out a way to do it though, I think you should have it start to download the trailers pretty much the instant you start the script so that they're completely or at least mostly cached by the time it gets to actually playing it. For those using the trivia clips, there would easily be enough time for it to download them all the way. I just think it would be a bit smoother, because you'd be sittin ghtere for like 15 or 20 seconds of a black screen while you waited for it to cache if it just did it when it got to it, and also, I might suggest trying to get it to automatically choose the medium video size, or perhaps make that a setting people can change in the file, because many of the "Large" quicktime trailers are SUPER high quality and lag like mad when the xbox tries to play it, even if it's already 100 percent cached.
Also, what exactly do you mean by "merge them back?" My "modifications" are very simple ones that are just for personal preference, changing the order of which videos it retrieved first and how long it did the trivia reel and so on