Whoever writes Ask MR should refer questions on operations to Jerry Dziedzic, because they generally muddle things up worse trying to wallow through it themselves.
The answer to the question whether a locomotive is able to have cars on both ends is very simple. It's "yes." Especially when switching.
If the train is shoving cars, then the crew has to make sure there is somebody protecting the move (a trainman has to be on the leading end in the direction of movement whenever it moves) to make sure the way is clear and all the switches are lined.
And the "engineer" isn't calling the shots on switching, the conductor or foreman is. Yes the engineer is jointly responsible for safety, but the person figuring out the moves is the conductor or foreman. The engineer follows trainmen's signals.
The comments about having cars on both ends on the main track overlooks that when trains do that, they have to have a person on the point, the leading end protecting the movement and in position to stop the train and flag crossings, plus most railroads have restrictions on the speed of the train when shoving cars. Obviously if you have a speed restriction on shoving cars, that means that its allowed, its just not efficient or easy for long moves.
Since the person who asked the question has a "small switching layout", that implies that it will all be short moves. Once again, for the circumstances the OP asked about, the answer is "Yes, its perfectly fine, just protect the shoves."
Dave H. Painted side goes up. My website : wnbranch.com