I appreciate all responses! I put out the list of all I would like just to see what responses I would get. I agree, the list is too much for the space. Yes I could stack levels, but I think it would be a bit overwhelming, both to build, but to operate too.
I agree the big passenger trains would overwhelm any scenes in 12x12. I am not happy with how I did the corners on the Ceiling Central and have seen some ways to improve them. I could make them a little wider to handle the big passenger engines and cars.