TBH, I think that gamemode you described could grow into another mode alltogether as sort of a Cops and Robbers mode. What I think that we're doing is to keep as close to the 2048 variant of Zombie mode as possible, so removing the cannon would just destroy the mode. However, I don't know a better option to help the speed of the mode along with keeping it in-line with the style of 2048.

Anyone have any other ideas?