It is a great idea. How many here remeber the series in Model Railroading (back in the 70's, under a different publisher) called the Time Machine? The idea was to build structures on a base that could be lifted right off the layout, and replaced with another. One had a water tank that could be replaced with a scene with the footings, some debris and weeds. Another was a station modeled with various changes over a period of time. A great idea for someone who actually has time to finish even one time period!