As pointed out, large Alcos (although it's been awhile) have been done, SD40-2 have been done, Alco RS units have also been done. I posted that the Baldwins haven't been done. Give me an AS-616 (or one of its several close looking brothers...DRS-6-6-1500). This is the largest model of locomotive that hasn't been made yet in N scale...
I've been trying to convince Atlas to make an AS-616 for years now (and with only a few changes, a DRS-6-6-1500) since they did make the Vo-1000. It's one of (if not the largest) fleet of locomotives not yet available in N scale with over 200 engines (plus another 80+ if you include the DRS-6-6-1500). C&O, Pennsy, and SP all had at least 10 of them. C&NO, Milw, and UP also had some in their fleet. With and without dynamic brakes, thin and thick frame, A and B units...