I wanna add on a few problems you may encounter and have to overcome.

As I said earlier you should make it scan the files before re-raring the files. Another problem if it's all automated so much is you'll be re-raring the original info file and url shortcut.

A way you could get around this is at the start be able to select Movie or Music when adding the links. That way before it re-rar's the files it could remove any files that are less than 500kb and not wmv / avi file types for movies or mp3 / wma for music. This way you won't be advertising other sites.

It's a lot harder to do this for apps and games as the txt file could contain install info or a serial or adverts for a website. Until you think of an idea of how to fix this it's only suitable for movies and music.

Another thing. After it extracted the files I'd make sure it checks that it doesn't contain rar files and if it does extract these do it's not double rared.

Maybe you could team up with someone as it's a big job although I do wish you luck.