GGG,
I agree 100% Lionel will make the interface, as time goes on and the people like us start asking for it. I actually think this is a Lionel long range engineering plan, Guns if I were you I would beat them to it, with a simple in-expensive transfer unit of some type. If I was an Electrical Engineer I would already be working on it. Heck Lionel might even purchase the engineering from you! Really like the simple Hand Held Remote for the kids, one of my 6 year old nieces was playing with my new Hallmark/Lionel Santa Toy Maker Express this afternoon and having a ball, the kid friendly Hand Held is a great sales tool, I would not eliminate it, I would do as you indicated and engineer some kind transfer box to allow additional Legacy control also. IMO the sales market would be there, I would purchase one right now, a lot of other owners would also.
PCRR/Dave