Will the enemies be ranked accoring to paper size?
Thats not a bad idea! But what about the old imperial sizes? Think of 'Emperor', 'Grand Eagle' or 'Double Elephant' as enemies. :)
And will it be a 3D or 2D game?
Two-and-a-half-D. I'm dreading endless comparisons to 'Viewtiful Joe' when people see it moving. But my original point of reference was actually the paper cut-out style which Ivor Wood used in the Paddington Bear animated series shown on the BBC in the late '70s. Mixed with a little of the Brothers Quay. And its not going to be all black and white btw.
Hope that makes things a bit clearer. ;)