I would love for a full complement of Box 2D physics functions, as alluded to already. Rojo's Chipmunk plugin looks excellent - when I tested it with moving on-screen sprites the performance was identical to C2's Box 2D. So, rather than ask Ashley to start over and try to implement yet another physics engine, I would rather that the missing Box 2D functions could be added instead - you know, weld joints, kinematic bodies, contact points, debug world rendering, and so on....