A quick, and not very thorough, internet search for pumps that move equivalent amounts of water as the bottom diffusers claim... indicates that the initial investment of just the pump would in the thousands of dollars. Doable? Yes, but how much can one's wallet take? I think a waterfall that "bounces" the water excessively could reduce the pump size since the aeration would be taking place on the massively increased surface area of the droplets compared to just bringing the deep water to the surface of the pond. The pump cost is still going to be considerably high compared to a diffuser based system.

Fish on!,
Noel