The control data alone can saturate slow connections if enough clients are in the game. Sending the game state only works for typical 3d games because they make heavy use of interpolation and prediction on the client side, and the host only sends the necessary data so that the client can render what it's player sees at the moment. That's typically a lot less dynamic stuff than is on the screen in a Clonk game: A few enemies, weapons and projectiles instead of hundreds of landscape pixels. So, while it might very well be possible to come up with a way to make this work for Clonk, it would be very, very difficult.