2 Attachment(s)
Found the solution, but changed my mind.
So after breadboarding, I'm seeing the speaker output is just way too dim for the main LED. It doesn't even light the whole blade. So I am going with the main green die off the board's LED (-) through the TIP42, and the speaker (-) for the amber flicker / red flash on clash. It actually looks pretty good. I also replaced the stock overly-sensitive swing sensor with these and put 2 at 90deg (2-axis setup) SW-200D motion sensor
In the end, and answering my own request, it seems the following works (in software anyway) to reverse the stock LED signal behavior for a flash-on-clash effect (turning an off-state into on-state). The switch in the schematic representing the the POSITIVE leg of the Hasbro board's stock LED.
Attachment 15338Attachment 15339