Here is an idea I've been toying with. In the drawing, the wrap-around backdrop, in green, is offset from the edge of the layout by several inches. Behind the backdrop is a staging track, shown as a dotted line. It enters the main layout area via a disguised area in the backdrop. The staging track ends in a "cassette" (shown as a rectangle, ala Iain Rice's "Small, Smart and Practical Railroads". This cassette is basically a removable section, enclosed on the sides, and with a coupler at the end so that entire trains, or sections of trains, can be removed and/or replaced en masse. It could possibly overhang the edge of the layout, by maybe up to 1/2 of its length. Any comments, questions, suggestions?