Another option, which I recently mentioned on another thread, is to make everything reachable by making portions of the layout moveable or removable.
In my case, I added a river between 2 plywood tables, resulting in a width of about 10 feet in that portion of the layout. 10 feet is way too wide to reach a derailment or otherwise make the layout fully accessible.
After having a long and narrow layout for many years, I liked the greatly increased depth, enabling me to have a lot more real estate for Plasticville and other structures.
The blue river filled the space that used to be an aisle from where I could previously reach all areas of the layout.
To make things reachable, I made the river using light weight 1 inch thick foam, and made it removable or moveable.
I moved the river about 15 to 20 inches creating the square shaped space enabling me to reach derailments under and near the window and to the right of the mountain.
Once the derailment is remedied, I simply slide the 1 inch thick foam back into position and re-decorate the river with boats, barges and lichen.
Arnold
