The 4-4-0 would be just fine. But Bachmann (or anyone else reading this) can tap an untouched segment of the 3-rail steam locomotive market.
Logging 2-6-2, 2-8-2 and the tank versions thereof.
Small drivers mean they are closely spaced therefore can go around tight turns. Large boilers can hide motors and the electronics we love/hate so much. Not to mention a not so small tender.
Saddle tank also helps with the motor, electronic board concealment.
Can be a 2-6-2 as well. Frames can be set up for 3 or 4 driving axles. The boiler can have an extra course added for 2-6-2 or 2-8-2 variants. Same with the saddle tank superstructure.
Just a suggestion. Small drivers, lead and trailing trucks, Something we never had on a 3-rail engine. Tank or tender, same chassis. Lots of bang for your tooling buck.
Logging, mining, short lines, museums all used them.
Bachmann has done a lot of logging/mining roads in their On30 line. So this is a natural for them.