The key element 3rd Rail has got going for them is a nice niche market for scale length passenger cars. The challenge as the scale length endeavor proceeds (and not just 3rd Rail) is there has to be balance i.e. you cannot make a beautiful passenger train and not have the right power to pull it, as such you cannot make gorgeous passenger power with incorrect passenger cars behind them. This in turn brings a whole new challenge as the cost of a new passenger train is in the 2 grand range. A pair of units is about $1,000. So it becomes a financial challenge for many folks due to the all at once delivery.
So for the Amfleet cars the key would be to hold the price down somehow, which means Golden Gate high quality injection molding. With careful engineering Metroliners and later Amfleet II cars could also be done. With the release there would be a need for power. Previous releases of correct power are AEM 7 and FL9. Those are hard to find and out of production, so next alternative is the future E8A. Amtrak had three E8As that were converted to Head-End Power (HEP) and the generators were installed where the steam heat equipment was at the rear. That would at least get modelers by for a while.
The Amfleet scenario would ultimately cry for new power and that would be for a highly accurate F40PH. The challenge would be the tank drive as F40PHs don't have tanks the full length between the trucks. Here lies a golden opportunity to do a high quality HO style tower drive and get away from tank systems all together.
So you can see the challenges of just doing cars or just doing locomotives is not an easy one. I would also encourage Atlas to consider doing scale length Amfleet cars and an F40PH. It would be a terrific compliment to their previous releases. One thing they've done well and Scott (3rd Rail) has too integrate post prototype scheme releases in their passenger product line i.e. California Zephyr cars in Amtrak Phase I paint. There is still a lot of opportunity.
I think a perfect train for Atlas or GGD to consider is the Empire Builder. Do the same thing Walthers did in HO Scale. Offer original GN, Big Sky Blue GN, Burlington Northern, Amtrak Phase I, and later special cars i.e. Amtrak full dome as used in Auto Train and other corporate functions.
The main thing is if engineering can start out correct in the beginning with an indoskeleton design where adding prototype roof, sides, ends, and underbody elements separately.
