It's been about a year since I've been to DEN and ATL, but DEN doesn't have any gates at its checkin/security building (unlike ATL's T gates) - thus in theory everyone who did not exit the train at A isn't going to be going to a gate.
However, I don't think you're necessarily forced out of the train when you arrive in the main terminal. I believe DEN (and most airport people movers) employ
Spanish solution platforms at the end point - that is one side of doors will open first to an "exit" platform that lets people out to baggage claim, while the other side of doors will open a few seconds later to a "boarding" platform that lets people in going to gates. Then the train reverses (switching over to the right side if necessary), going back to A/B/C - thus there's no "repositioning" to worry about. Presumably all you would have to do is not exit the train and let everyone else board, and go with them back to A/B/C.