WOW!!! there are a lot of great ideas out there!!! There is definitely a market for the 4-8-2 and 4-8-4 out there! And the switcher's 0-4-0 and 0-6-0! If Lionel played it right, they could create the die's that would allow for the scale size, detailing and full Legacy control, then a simplified version for the less expensive sets and individual sale. (Or are they already doing that??? ).
My wish would be for The Reading T-1 4-8-4(scale, detailing & full Legacy), Delaware & Hudson K-62 4-8-4(scale, etc. etc.). And C&O's Greenbrier, but the original group(600-604) as delivered from Lima(1935)(scale, etc. etc.). Love the idea for BM&R(R&N) #425 Pacific.
The idea posted by another individual for a "Series" for Excursion Locomotives and associated rolling stock is a fantastic suggestion. Lionel might be able to roll with that 'Series' for a while. There are a lot of great steam engines 'to be modeled!'
How about the ALCO C-430 (scale, etc. etc.) Not to forget the C-630 and C-636 (and/or their Canadian counter point M-630 and M-636). I agree on the RS-1 (WWII).
Hmmmn... How about Baldwins RS-12? Or couple of Lima-Hamiltons switchers (sorry... brain cramp right now, can't recall the model numbers....)
The hope that Lionel will start manufacturing their products here in the USA again. Like others, I know this propably wishful thinking. But, the Presidential Box Cars are a starting point.