Andy:
I'm going to disagree with you about the item in the picture. Unless RI called it a doodlebug for their own reasons, I think its a locomotive.
But, man, what you have in your picture is something even rarer than a doodlebug. RI had 2 E6 B units built with a baggage compartment inplace of one engine, a cab and a headlight. The unit ran behind the regular locomotive, but when the train split, the B took one section while the A took the other. The idea was that the B unit would fit into the streamlining rather than running them nose to tail.
(details from the Diesel Spotter's Guide)