Jon,
Thanks for asking about this topic. Here is my opinion: I could would be fine with either the single motor configuration you mentioned above or having command and two motors in one unit and the railsounds in a dummy B unit, similar to the way the PWC style F-units are set up in 3 rail. In the case of a GP 7/9, I would buy more than one anyway. If a GP 7/9 is on the drawing board, if it can be made with the same level of detail as Lionel's O scale verisons, then I wold say that it would be a home run!
In regards to DCC, personally, I have no interest in it whatsoever and would go out of my way to avoid using it, but can see the appeal to others who are in need of a common control system to run Lionel's new products and their existing trains.