A lot of folk have quips about the ideatron limiting creativity blah blah, but I feel this is a perfect limitation for this competition, and it limits the coder to the time constraints! (you can't really gamble with setting up a generic box2d game and re-skin to the theme of 'summer heat' ).
I think seeing games made with an interesting take on thier crazy theme is much more impressive then taking something like 'summer heat' where theres no limitation, its just 'make a game of any sort and make it a bit sunny'.
I understand not liking the idea of the pre-determined teams. I'm all in favour of the randomness. But with a skew involving much less coders there's a chance i wouldn't make ateam, so I paired with a friend. Maybe there could be a 'primary/secondary' skill you specify for the randoms so if there are too many coders. Ones that are profficient at doing at art can be put on a team as an artist.
Of course you'd need coders compotent at art for this though!
Totally looking forward to seeing Punk Rockers Kicking Big Opera Singers