As long as you brought it up, you hit the nail right on the head! Gleaner's cleaning system does exactly what you are looking for. Never been a simply designed shoe that works better than the Gleaner!
The old 1963 C2 Gleaner had TWO fans,The young polaroid engineering department at DEERE apparently haven't seen those old pictures. You might consider putting a dust diverter blower under the pre-cleaner to lift the chaff and get the cleaning started