The Lionel S gauge engines have truck (or moving pilot) mounted electrocouplers. Almost all American Models engines have fixed pilots and the couplers are body mounted using a short mount arm. I have electrocouplers on my AM steam engines. There is obviously no pilot to deal with on the tender but the couplers stick out unprototypically far.
I have never tried to adapt an electrocoupler to an AM diesel. The easiest would be a Trainmaster because it has truck mounted couplers. All my other AM diesels have body mounts, it will be a challenge to devise a mount.
My AM engines have ERR TMCC and Railsounds boards retrofitted. The ERR TMCC board has outputs for front and rear couplers. I am not a DCC user so I do not know if DCC boards have coupler outputs. Most DCC operators use Kadee couplers. I do know the DCC system is coupler capable because all the Lionel S gauge Legacy engines also operate on DCC and the couplers can be actuated.