Well here's a bit of an off the wall suggestion, but how about the Amtrak E60 and E60MA?
We have only had the semi scale Williams engine offered in O gauge, and I belive that neither MTH or Lionel will want to tool up for what is a regionally popular locomotive, which would make it a good candidate for Scott to offer.
It would also go nicely with his scale Amfleet cars due out soon.
Here are some sample photos I found in various searches as I have been collecting photos for a modeling project, but they are not mine.
The E60 as delivered in 1975:
The Rebuilt E60MA in phase 3 paint:
They were also used by New Jersey Transit, NdeM of Meixco, and the Black Mesa and Lake Powell Railroad.