There are a couple of German locomotives from the DLS I have, (I think these are for 2006 and 2009)
BR118_V4_EBW and also LOCON and WAB
also a DR_BR110
These have the ability to turn off the engine by using the Pantograph key in Driver
Maybe you could take a look at them.
My two cents here. Good luck.
Warning, they have an emergency shut down system that should be unchecked if you don't want warnings all the time while driving along with shut downs of the engines.