There's always the option of doing a hybrid layout -- a 3-rail layout designed to 2-rail specifications as to turnouts and curve radii. Using insulated track such as Ross, Atlas, or MTH ScaleTrax, you could wire it to support both types of operations. The restriction would be that you couldn't use #6 and larger turnouts without some modification to the frog. If using Ross turnouts, they offer a #5 (AKA 11-degree) which seems to work well with the 2-rail equipment I run at the club
Just a thought.