To be honest,if you are right; what I suggest can be used for almost anything running on 16.5 track. The only problem I see is the size of the bolts above the piston however nuts n bolts come in all sizes. As for mass production; well if a product like this came on the market, I would require 6 from the start because ther are lots of small locos that I would love to model.
Geoff   

Hi
I am trying to model something unique; The Saundersfoot Railway 0-4-0 loco, Bull Dog. The railway is 4 foot gauge and I am using 16.5 gauge tracks @ 4mm scale. The loco stands 6 feet high and in 4mm scale is less than 1 inch high.

I am using the On30 porter loco as a basis however because the Porter motor is on the top, the height of the model is just under 1 ½ inches, about 9 feet in real life; still small for a 4mm or 3.5mm scale loco.
 
Has Bachmann ever thought about producing a steam type power bogie because I think that there could be a big market for such a product?

I was thinking that if the Porter wheels/ motion/piston were used and an N gauge double ended motor fitted between the frames powering both axels; this would bring the centre of balance down.

The chassis could be used by the modeller for 0-4-0 industrial steam locos in 3.5/4/On30/7 and Gn15 scale models; with the modeller building their own body; if two chassis were used together forming 0-4-0 + 0-4-0 could make any form of articulated locos.

I think that the above chassis would enhance the fantastic range of locos that Bachmann make.