One possible reason for no UP RS3 is that the UP never owned any. They bought RS-2 and RSC-2 units. Granted, the lack of a prototype has never stopped a model manufacturer from coming out with fantasy units, but just because they can doesn't mean that they will.
![Wink ;)](https://www.bachmanntrains.com/home-usa/board/Smileys/default/wink.gif)