Wouldn't it be nice if you could get a poly insert for a gravity box so you could haul liquid fertilizer to the field? Gives it a new use and most people have them. No need for a separate nurse tank and wagon. Gravity box sits and does nothing for 11 months of the year anyway. Put a vent at the top and have the bulkhead where the spout is. You could mount your pumps on either end of the wagon.

Think this will fly or crash and burn? What do you think?