Use the coal tender to hide the Li Ion (18v) rechargeable battery.
Charge battery with water tower spigot or a docking port of some type to easily remove battery pack.
Beef up wiring harness/connection between tender & engine
Use IPad for control
No track wiring needed and track can be 2 rail.
Have no idea of motor current needs without some measurements
But I think something like this is coming
Possible or unrealistic?