The 3-4 isn't about height and weight. Sure, those are part of the equation, but the true KEY to the 3-4 is DECEPTION. And skilled linebackers.
For the 3-4 to work well, ALL four LBs need to be able to stuff the run, rush the passer, AND drop into coverage. Even in Nickel, you have three LBs on the field and one of them rushes. This usually puts the other two LBs in coverage or maintaining their areas of responsibility. On any given play, the offense isn't supposed to know who the fourth rusher is, or who the Mike is. This is what makes it so good.
There is one very simple reason why OUR version of the 3-4 didn't work very well: DeMarcus Ware.
On any pass play that mattered, the opposing offense KNEW who was rushing, so the only deception that we had left was to blitz or not.
Today, we would be in the same situation due to Micah Parsons. He WOULD be the fourth rusher and everyone knows it. So if the main advantage of the 3-4 is deception and that is off the table, what's the reason that you want Parsons further away from the QB?