You can.. but that's not realistic. In order to improve an OLB's overall rating, you'd have to increase a bunch of stuff that only makes sense for a 4-3 OLB like man coverage, zone coverage, etc that would completely change the ability of the player you're putting at 3-4OLB. The point is, a different skillset is required for 3-4 OLB, one that is simillar but not the same as, a "Pass Rushing" DE in a 4-3. Changing that many variables would ruin the game IMO.