Well to be honest I don't have a need at the moment until I take one of my tanks and FX5's over to my mother's home and set her up with Goldie's. But in reality its an already proven system commonly used system, all I did was merge the two and all the FX5 is doing is filtering the sump like any other aquarium, so it has to work.
But yes one reason I came up with this was so that I could 2 tanks off one FX5 using a small deep high water level (50%) sump. The concept is no different then using a heater or UV sterilizer in the sump rather then on the aquarium.