We have touched on the scale vs high rail decision in S gauge. I would pay the price but with 36" minimum radius curves it will not run on my layout. I have a lot of 30" R curves. I would seriously doubt Lionel would ever bring to market an S gauge engine that will not operate on Gilbert track or the Lionel S gauge FasTrack. Also like the majority of S gauge operators I do not use DCC. In order to sell more that about 70 to 100 units of any engine the engine would have to be able to work with AC track power and the Legacy control system as well as run on 20" radius curves.
Well, my scale code 100 curves are 33" radius and 29" radius on the passing sidings. There is scale equipment that can't take those curves, my SP MT4 (4-8-2) for example. I suspected it wouldn't when I bought it, but it is such a nice locomotive...
But that hasn't stopped me from enjoying S, I just run my smaller power. My AM Santa Fe Northern's will take my curves no problem, but look a little awkward doing so.
And while I do have a DCC system wired into the Great Plywood Glacier, most of the time I run conventional DC. Again, running conventional DC hasn't stopped me from enjoying S.
I also have MTH's DCS, Lionel's TMCC and conventional AC from my O gauge misadventures, which I use on my Christmas loops. And FlyerChief is sorta neat, simple command control without needing an EE degree to get things running.
As a sidebar: One thing I noticed is that 3-Rail O really took off when it broke out of "O31 thinking" and stated offering locomotives that required larger curves. Kinda counter-productive thinking to be sure, but if 3R folks wanted to run the larger stuff, they rebuilt their railroads. It seems like many S Gaugers will only part with R20 out of "their cold, dead hands."
Now, Lionel has managed to get everything to go around R20 curves so far. Awkward, but operational...
Both old and new Flyer Northern's run on R20. Even the AM HiRail version Northern will do R20 as will the rest of their product line. Everything SHS made handled R20, as will the MTH F3's. So that's not really an issue, at least not yet. Although, there might be an issue with switchstands and some rolling stock...
R20 isn't really the problem it's sometimes made out to be.
So, would a FlyerChief or Legacy an NYC J3 bring in the masses? No. It would make the most of the current customer base rejoice, but have little effect outside of S. Would any one specific locomotive bring in the masses? Again no.
The problem rests with our beloved suppliers. American Models has been the one consistent thing in S for the past 30 years. But, I guess their products are simply too boring for today's market being conventional control and an out of date sound system.
MTH is wandering in the desert and Lionel can't really make up it's mind what it wants to do with Flyer. For now, it seems Lionel's sort of settled on upgrading traditional Flyer with occasional gusts of Legacy. But, if there's another management change in the future, all bets are off.