What you're describing with airplanes already happened. Large airplanes used to land on the water, which incurred a mass and aerodynamic penalty for the airpla

What you're describing with airplanes already happened. Large airplanes used to land on the water, which incurred a mass and aerodynamic penalty for the airplane but was very cheap to operate airfields ("fields"?) for; it only required a flat lake or harbor which was already there. The switch to landing gear allowed airplanes to be more optimized but requires more infrastructure expenditure for large aircraft.