This is an interesting topic. When it comes to championship venues and older, classic courses, the width of the fairway has always been the area of my greatest concern in the tournament setup.
It just doesn't seem appropriate to me that the rough between the fairway bunkering and the fairway should be the same penalty as that around or outside the bunkering. A shot a couple of yards out of the fairway but inside the bunkering should not be penalized the same as a shot outside the bunkering, and the idea of a shot hit off line enough to reach a fairway bunker being a better situation than a shot just missing the fairway, but inside the bunkering, just doesn't make sense.
So, your question on whether to expand or move the bunkering is a relelvant one. I personally would adhere to expansion of the existing bunkering toward the fairway. The only problem with that approach is the altering of the scale of the bunkering. Although I wasn't at Bethpage, it appeared that that is what happened, and from pictures, the bunkering appeared a bit incongruent. That might have also been the case at Oakmont if the bunkers were altered to fit the fairway width. I would have preferred a shorter rough between the bunkers and the new fairway line. Enough to affect the spin the players could put on a shot into the greens. Not chop out when 1 foot out of the narrowed fairway or step cut. Just mho though.