Let's make this interesting and say it cant be Ladanian or a QB. I think I might go with Marcus Cannon or Jr year Tommy Blake.
Mike Freeze
If I had to pick a LB I would love to see LaMarcus McDonald run around with the current DLI'd probably go Jerry Hughes. Although Cannon is a really tempting choice. Would consider Daryl Washington also
If we think our QB play is decent, I would argue the answer may be to get our best OLineman. How good our OL seems to be has such an impact on the quality of our running game which then impacts our QB play and passing game. Given that we have some good running backs coming back and some good receivers, it would make sense that adding a top quality tackle or center to the mix would ensure we get good results from the running game which would then lead to improved results with the rest of the offense. One thing other people's answers are leaving out is that its an open question of how Boykin or Doctson would be without the other and how LT would do in a spread offense that didn't strongly cater to the run game as his TCU teams did?