The well deserved hype around the East Broad Top these days I believe makes the next obvious big On30 seller any EBT model. The locos and the doodlebug would go great on my freelance layout.
While I agree that any EBT locomotives would look great in On30, I also wonder how much of a market there'd be?
They'd be much longer than the ET&WNC-pattern ten-wheelers, which might scare off many into On30 (as many in that gauge want as short as possible to negotiate tighter curves).
For the same reason Bachmann never made any of the post-1900 D&RGW engines (like a K-27 or K-36, which were monsters in size for narrow gauge), that's why I wonder if you'll see a EBT "very light" Mikado. I couldn't find anything on their exact length, but I don't think they were terribly short, which would mean they'd need to broader curves.
I agree that the Bachmann On30 equipment is intended to run on the tight 18" EZ Track, and therefore needs to be short and compact. The most likely candidate among the EBT locos is 2-6-2 No. 11. Imagine Mike No. 12 cut down one less driver set. She was sold off the EBT during WWII, destination unknown, and hadn't been in operation for a number of years before that.