The HO scale 0-6-0 chassis is available and would make a fine starting point for a new On30 locomotive from Bachmann.  New superstructure but no development costs for the running gear. 

As for the existing 0-4-0's and 0-4-2's, swapping around headlights, stacks, etc. and adding some Grandt Line details like round sand domes and Banta wood cabs have providing me with a variety of small steamers.

Very nice work!

You are right!  that would be an awfully BIG locomotive!

I bought one last year when I heard they were out of production.  I am back dating it with a Banta wood cab, modifing the lights to oil lamps, link & pin couplers, etc.  Makes a great little 20.3:1 engine for small four wheel cars.

I have added Bachmann decoders to both the 2-6-0 and 0-4-0 Porter.  It wasn't particularly difficult, but deffinitely not for the faint of heart.  At this time I have two 0-4-0's apart in the process of adding decoders.  I also rebuild the headlights for surface mount LED's.  I remove the cab lights and contacts for them.

I haven't yet seen the new lowered cars.  It sounds like what many have been doing on their own.  Removing the raised bolster on the truck frame.

Jim P