First and foremost, I would go QB at 4. You can't win in this league with a crap QB and the Cowboys are staring down the barrel of a Romo-less future. So I would absolutely go QB without hesitation if I were Jerry and my scouts were saying Goff or Wentz have the potential to be a franchise guy.
Second, if the QB was a non starter, I'd try to trade that pick. I think this a fairly deep draft on defense and if I could slide down a few pegs and pick up an extra #2 or more.
Three, I'd go defense. You can't build a great defense without elite talent. So I'd look at Ramsey or Jack in that spot. Two uber athletes that bring flexibility.
Four, why I wouldn't go Elliott at #4? We've invested heavily in our OL and this league has shown that lower round picks and even re-treads can have great success in running the ball in this league and that you don't need to blow a Top 5 pick on a TB to have an elite running attack. I am not opposed to Elliott at all. Just not at 4. If you could get the Rams to give you their 15th and and 2 second rounders, I'd have no problem then taking Elliott at 15 because then you have three #2s to strengthen defense. But Elliott at 4, with the holes on defense and the lack of any contingency plan at QB would be insane IMO.