the concept is simple : remove the ability to remote control by default, and have a gadget that adds the functionality to anything its mounted on. The DVRT likely doesn't have the money to implement RC on EVERY single BE2, DE2 and DH4, right?
to be more specific, have a gadget that's like a receiver, with an adjustable antenna, and have it compatible with the remote control. It could have "REMOTE CONTROL EQUIPPED" written on it, as its intended to be fitted outside, since it'd lose signal easier when it senses its inside, along with a lower antenna. For novelty, it could have a small delay and beep every time the remote control 'sends a signal' to it, I.E. when the throttle is changed, brake is changed, etc. with a button to toggle a quiet mode where only the delay is present.
if possible, it could have its own beacon, or be able to output to something else that could act like the beacon. It'd be at 0 input at default, but upon something being inputted into the receiver, it'd change to 1, and once the locomotive is stationary or nearly stationary for 5 minutes or so, the receiver's 'to gadget' output changes to 0. Could also work with a possible universal bell gadget, but that's not the point of this suggestion. The beacon/'to gadget' output could also be toggleable on the receiver itself, either having a "active, or decided by receiver, or off" option setup, or "decided by receiver, or off" option setup.
this would make the remote control less of a universal thing, and more specific to the stuff the owner owns. Ofc, gadgets still work on DVRT-owned stuff, but its a waste at some point, unless you uninstall them from the locomotive.
the image provided is simply an example of a remote-controlled switching locomotive, representing that remote control is something intended to be noted of on a locomotive.