So the idea, for me, is a drop-in, DC motor, with the form of the open frame motor, that can be speed-controlled...such that you unbolt the old pullmor...drop in this new DC motor...connect it to an err/3rd rail motor drive/back-emf speed control board...and for all intents the engine retains a vintage appearance but runs like a modern engine.
I have no doubt it would not be a financial failure...more of a money pit based on the niche it would appeal to...but there are a bunch of engines out there that could potentially be modernized to run in a more true to scale manner than just running like little speed demons...
If I won the lottery, this is indeed a project I would take on...consider it a loss and a tax write-off...and a gift to myself and my fellow hobbyists...