The CNJ certainly excelled in areas of unusual first generation locomotives as did their fleet of steam locomotives up to the early transition to diesel which was completed in 1953. Personally I'd like to see a Baldwin DR 6-6-2000 on my layout someday. I assume there was a brass model made at some point, but I haven't found one.
On the steam side the widespread use of the Wooten firebox makes many classes of their steam fleet hard to find as well even if many were based on Reading designs. The Camelback 10 wheeler is an easy find, but the Atlantic class Camelback is non existent along with the the 0-6-0, heavy Mikado, and several of the Pacific classes. In many cases, 3D printing the firebox and the cab to replace a mass manufactured USRA type would make for at least a reasonable kitbash.
The FM models have been done extensively for many CNJ prototypes, but none every done exceptionally well although I have a K-line H24-66 to convert one day and the Lionel H16-44 was done well outside of the floating trucks, high ride height and the 3 rail accommodations.
Speaking of rare diesels - a bit out of era, but I would like to bash or prototype an accurate SDP40F some day. The MTH Scaleking models fill a gap, but are wildly inaccurate in several areas.
