My high-level, overall plan is to build a number of stand-alone dioramas. Each diorama can consist of one or more modules; whatever it takes to build a single scene. To build a more complete layout, I would connect these stand-alone dioramas by using either pieces of flextrack (visible or hidden) or more complicated connections, such as shown in the accompanying diagram.
I use the term "module" rather than "section" or "sectional", even though I am not building my dioramas to a known standard. The word "section" is too over-used, so to avoid confusion, this web site will refer to each stand-alone unit as a module. One or more modules can be combined (i.e. placed adjacent to each other) to form a cohesive diorama that depicts a modeled scene. A collection of dioramas can be put tightly or loosely together to form the more conventional model railroad. While I am building individual modules, it is not my intent to just have a collection of random modules sitting on a shelf somewhere; I do fully intend to build a more conventional model railroad composed of these modules, to operate and run trains on.
After years of trying different styles of layouts, and after learning about what I enjoy and what I don't enjoy, here is a list of the reasons for why I chose this method of construction.
So, a simplified version of my plan for my (future) layout is shown in the diagram. The green rectangles represent dioramas. In this concept drawing, they are placed in a corner, and the corner is occupied by a loop of track or an over/under helix. The idea here is that a train leaves one scene (or "stage") and doesn't re-appear into the other scene until some time has passed. This corner loop would be hidden from the normal operating viewpoints, but would be accessible via the back of the layout, for example.
And, of course, stand-alone dioramas could simply be connected with pieces of flextrack when they are placed next to each other in line. This allows me the freedom to model any scene along the branch line that I feel like building, without having to be concerned about it connecting to the next scene over.
The plan is to keep every single module I build over time. I am done with taking layouts to the dump. So, this is my permanent and last layout, which is going to take me decades to build, and will move with me wherever I go.