Joe, please don't give them such ideas! If the railroad cars have seat belts next year, we'll all come after you with extreme prejudice... :)
Actually, something I have seen on a train...Oaks Park in Portland, Oregon has a Chance CP Huntington train. They've put little hinged doors on the side of the train to discourage kids from climbing out. Cedar Point merely recommends that small children sit to the inside (where they can't see anything) but then, those coaches are large enough that inside seats actually do exist.
Because the spacing between benches on the CP & LE coaches is consistent, it wouldn't be too terribly difficult to come up with a sliding door arrangement, something like the doors on a Huss Ranger. But knowing the way CP does things, I doubt we will see that happen unless there is a terrible accident on the train. I mean, after all, to the best of my knowledge they haven't lost any kids yet.....!
--Dave Althoff, Jr.