I absolutely think that doing something like situationally could pay off. Flip from a 3 to a 4 depending on down and distance. But, you can run into issues subbing there too if the opponent is going no huddle. IMO the best way to do this would be to have a versatile SAM LB that can play in space, but also put his hand on the ground and play RE. That's probably McLaughlin, but could also be Kenard Snyder? Of course, if a team is huddling, you can mix and match however you want.
I just think that Campbell has said pretty much every year that we will see more 4 man front and it never really happens for whatever reason. Our depth chart has had 4 DL positions this whole time. Guess I'll believe it when I see it.