I have a product suggestion. You could make separate sale buffer cars in the current big roadnames. Preferably, they would be airslide hoppers (MTH wink wink) or PS-2 3-bay hoppers as those seem to be the most common cars used for this purpose. Some could have an ETD, and some wouldn't. These would be a great complementary product for the Lionel 30k gallon tank cars. Lionel has already made 2 for their BNSF ES44AC OIL TRAIN SET, but they are hard to find. I think they would sell well as Tangent Scale Models in HO has already done 6 runs and they are all sold out (Run 1, Run 2, Run 3, Run 4, Run 5, Run 6). Further, buffer cars have also been brought up on this forum before (1st time, 2nd time, 3rd time). So, people are generally aware of what these cars are.
Below are some reference images:
(credit Matthew Schimmel)
(credit Ken Ziegenbein / thundertrain.org)
(The other RR's don't have specified buffer cars like the BNSF does, so finding images of them is harder, but they all have to use them on hazmat trains between the locomotives and the tank cars, so there are plenty of video examples out there.)