pass that sugar baby.
Also, I think the video series idea is really cool. I know I'd be into watching it.
As for song selection, I kinda like the here's your song deal with it kind of thing. However, I do see times where perhaps that may not work out to allow each competitor to be at the top of their game. So perhaps a possibility is to allow for a backup source. Such as, you roll for the source that would be chosen, and then the editor is given a backup source they can choose from their list as well. Then when the song is revealed they can then decide to use the given source or their backup, as perhaps the backup may allow them to produce something better then the rolled source. However once a source has been chosen it would still be thrown off the list for future rounds per normal (this would also stop someone from always falling back onto 1 series that they know really well.) Just a thought on that.
As a second suggestion, perhaps delving into more Royalty Free or Creative Commons type music would be an interesting change of pace. Stuff from say
http://freemusicarchive.org as possible choices.
For themes I really like taking a popular video and working with that song to see what kind of different approach you could make with it. I can't really think of any other themes without getting too specific and granular like Iron Editor or AMV Wars themes can get.
it's on like donkey dong 
