Well, four feet is around 12-13 40 foot boxcars, and that's not allowing for throat. If you split it in half and attach each half to opposite ends of the layout, there's not going to be a whole lot of track left to do anything functional. At least, not without more modules to extend the yard tracks.
Just out of curiosity, if you're going to scenic the area, why not just plan a functional yard? Especially if you only want three staging tracks, why not double-purpose those as A/D tracks and include classification tracks too?