Cool idea! As some others have mentioned, there were a few bugs (like the recoil problem) that made it less fun. In addition, I think it might be interesting to give the player a warning (maybe a subtle countdown effect) when the gun style is about the change.
It might also be fun to go all-in on the franticness: make the weapons change faster, make the zombies faster, make the player faster, etc. And some obstacles would help with positioning.