John, you could splice this in, but....the operational wiring is significantly different. The tender harness where the circuit board is, feeds inputs to the transmit MUX.
The Receiver MUX in the engine takes in these inputs and then manages the extra light. Additionally the MUX does the conversion for PV vice the diodes on the PCB at the back of the engine harness.
5VDC also comes out of it for the tach, and you need another connector for the output of the Recvr MUX.
Even so, this really only gets you one additional light control. The cab and fire box are one circuit and the headlight is the other. It does allow the Marker to be feed also, but I don't believe it is controlled. I need to check that.
So your looking at quite an expense and labor to activate one additional light feature controllable via DCS. Why not run a single wire with a connector to gain the firebox/Cab control.
The other way I approach this, is to see if I can fit the board in the engine first. Even some of the RTR have the board in the engine. If so, then you have full features like a diesel with a supporting sound file. G