I found these photos on another site awhile ago and was wondering what ever happened with the project. Building things that animate is my favorite part of the hobby and it is always fun to see what others are doing along the same vein. As far as marketability, there seems to be a demand for rotary dumpers and rotary couplers. I have heard the old Walthers kit fetches up to $80 or more on Ebay. With your CNC cut ends, bearings all around and quality that seems to be shown, yours will be severl times that amount. The high price and lack of rotary couplers will no doubt hamper sales but some will sell for sure.
I built up one of the Walthers ones to animate but it has never been incorporated into a layout. People seem to be impressed when I show it operate though. Knowing the limited durability of the plastic parts inspired me to cut new ends from aluminum but they are not as nice as the ones you have done. There are photos on my website in my signature.
I have a couple questions though, how do you keep the dumper centered on the rollers? How does the clamp system work? Is your prototype a Heyl-Patterson?