You will see some teams put a big O-Lineman along the DL on short yardage/goal line situations occasionally, but I haven't seen it done for an entire series or game.
As far as Kelly Griffin goes, I think he is a good player, but I have a buddy who watches the DL closer than I do who has been saying all season that Griffin is the weakest link on our defense. He says Griffin is a serviceable starter but doesn't stand out much over the backups and we shouldn't miss a beat with Coleman in there.
I hope he's right, but honestly I don't know enough about the two to say for myself.