Always glad to hear about animation challenges 
IMO we should stray away from movie quotes since that’s 10secondclub’s thing. Short character driven exercises would be great. Like:
[ul]
[li]Listening to a joke and then laughing.
[/li][li]Hear a rude comment from a stranger and slapping them.
[/li][/ul]
These could probably be done in less than 10 seconds. Why don’t we call it our LessThan10Second Club? LOL 
Personally I’d like to go for a quantity of quality… What I mean is that the challenges are short (like you can probably finish in a week) but really push to make it your best 5 seconds worth of animation ever. And have the deadline be 2 weeks.
Another suggestion I have is to do “Masterpiece” studies. Take a short clip from a favorite animated movie be it traditional (101 Dalmations, Tarzan, etc.) or 3D (The Incredibles, Ice Age, etc.) and try to copy it frame by frame.
Animation teams sound great but definately on the difficult side. I’d like to learn what it takes to be an animation supervisor myself.
Seriously, I think someone just needs to pick a topic or theme from a hat and just start the challenge. BTW Those guidelines sound great dalmanna.