Nearly all fairway bunkers should be CLOSE to the fairway. When you see one that isn't, 98% of the time it's because the fairway has been shrunk or realigned over the years, either to save mowing expense or to make the course harder via narrow fairways and more rough.
However the surest way to integrate fairway bunkers is to not build so many of them. Perry Maxwell, to name one architect, typically built only a few, and nobody thinks his courses aren't testing enough as they are.