Well, improvement would be allow continuous "fire" with it and movement. Or introduce advanced watering tool that allows that as upgrade to it, while keeping the wooden watering can as it is and being requirement in building the advanced watering tool.
The watering can right now is fairly difficult to use, even though its just a watering can. The can should allow you to move and have a much higher "fire rate" because now its very low. Really the spread is unnecessary if there is a higher fire rate
