I know about BlueRail, I'm getting their product update notices. I'm not really interested in that until it reaches critical mass. Also, I would have significant issues trying to sell most of my customers on that option.Are you familiar with BlueRail. They make a 5 amp board for O-Scale controlled by a phone app. And they have a DCC decoder option board. At present, they only support IOS. But with MTH gone, they may be a viable conversion option. Adding an Android app is a must. Not sure about the other features they'd need to offer. That's your expertise (do I hear consulting fees ).
Given your side line is repairing these locos, perhaps starting a dialog with the company could "start the ball rolling."