As someone who finds it difficult not to be attracted to railway modelling and who finds inspiration in a variety of places, it is very difficult to fix a layout into a time and a place. Now one solution to this would be to build smaller layouts and have a number of them that are all from different locations, eras etc. The down side is that making small layouts can be very satisfying during the building process, but often leave you underwhelmed when it comes to operation. I am a great believer that the thing that sets railway modellers apart from other disciplines is the ability to illustrate the operation of the railway. Not just movement but in essence the "why" the railway did what it did, the way that it did. So operations, I believe are very important.
Another option is to make the layout suitable to use with more than one set of stock. Now this is possible do do in terms of time period but is more difficult to do in terms of location. A good illustration is Portchullin which sets out to represent the Dingwall to Skye Railway set in 1973 (and does a rather fine job of it IMHO) but also takes a turn of running Highland Railway and LMS steam locos. The scenery however would restrict further flexibility by being too easy to place geographically. Making a layout "generic" is extremely difficult if you wish to build it with any degree of prototype accuracy. Many railways had little idiosyncrasies or tell-tales such as track layout, buffer stops, signals and of course architectural features.
|This Sulzer Type 2 sits comfortably on a layout that could easily move 10 years back or forward without much loss of fidelity to the prototype. Steam through to BR Blue.|
By selective decision making it is possible to have a more fluid time period running on a layout that is large enough to provide operational interest. The choice of track (timber not concrete), semaphore signals not CLS, traditional buildings not boxes and signs and details that allow flexibility are all tools in the modellers box of tricks. Even some of the stock can carry over from one period to the next. The key I suspect is detailed research and discipline. Unfortunately I'm pretty good at one and pretty awful at the other!