I know it's overly simplistic, but I've never understood why, with 22 positions between offense and defense, you couldn't employ the model of taking one person to fill every spot slot each cycle (5 OL, 4 DL, etc..). You'd still have 3 spots open to fill positions that open up or to give to that rare specialist that warrants a scholarship (sorry, Volatil!).
Then, theoretically, barring horrifically bad luck (like we had last year) you'd always be between 2-4 deep at every position (2-3 deep at positions where you've had season-ending injuries or defections). It's always confused me how we get into a position where we need, for instance, 3 running backs in one class...seems that sort of scenario is going to strain other position groups at some point.