Can't shake the idea of converting one of these to a battery-powered model using one of Northwest Shortline's (NWSL) Stanton powered trucks, thereby completely opening the passenger section. Even though the model is typically short of most prototype lengths for this style doodlebug, it would be a worthwhile effort...IMHO.
The Stanton drive is far from competing on traction power with traditional OO3R/O2R drive systems. However, the doodlebug was never intended to be a major hauler of much more than it could carry itself. I have a Ross/Gargraves layout whose rail cross-section has enabled me to successfully run a dozen or so freight/caboose cars with O2R trucks. Sure, there's a bit more weeble-wobble as they traverse switch frogs, but, strategically located in a train (i.e., towards the rear of the train) they've never derailed...so far.
One compromise that might need forgiveness is the comparative wheelbase between the MTH/Lionel doodle and the available Stantons. The model currently measures out to about 8'-3" (from the all-important sideframe journals). Stanton's closest available O scale option would be an 8'-6" wheelbase. Not sure how much of a distraction a scale 1-1/2" misalignment of sideframe journals to the Stanton wheel positions would be.
OTOH, it might be worth the (very reasonable, IMHO) price of one to evaluate both power and appearance issues. If need be, perhaps using a Stanton drive on both trucks might be a further consideration to produce a better hauler.
NWSL's website indicates they also may have O3R wheels. Not sure of the flange dimensions. But I would imagine it wouldn't have to be much of an increase over the NMRA RP25 contour to provide an extra measure of tracking on Ross/Gargraves rail, at least.
In any case, it sure would provide some better interior detailing options than presently have to be overcome.
BTW, in my dark-side days (HO), I employed a Stanton drive conversion to an ATSF Hallmark doodlebug model...largely of necessity when the geared truck block froze from the dreaded ZINC ROT! Took some finagling, for sure, but was VERY successful...especially with the addition of DCC, sound, LED lighting...and a custom paint job!
Hmmmm... Need to keep an eye out for a suitable MTH 'dummy doodle' (ATSF, preferably). This might be the time to get adventurous!
KD