"A movie would be the same. THIS is how they look, THIS is how they sound, THIS is how they move, etc."
Agreed on all but the first point. It's not like we don't already know what they look like. My concern is finding actors that actually look like the characters. Wanting Orlando Bloom and the such is fine, but do these big Hollywood actors really look like our favorite group of 16-year-olds?
I could, however, see an animated movie/series/what have you. The oly problem is... you guessed it, voices. But as lond as Dan picked the voices, I'd be fine with it. They are his characters.