You don't want to place large buildings in a way that they will obstruct the view of the details of the layout... For instance, if you placed one large building in your scene in the center of town, you obscure the rear portion behind that building from various angles the people have to look at your scene...
Excellent suggestion. We need to assume we will have a back wall for the booth. Taller stuff should go in the back. Maybe we can even print out a forced prespective backdrop so the tower still looks like its in the middle even if its in the back of the model.
I was thinking that there could also be a set of bars going over the top of the dio in order to hang small micromachine ships from it for scale. It would be cool to have some air traffic in the proper scale.