The only part I agree with the OP on is that a change is needed. Not necessarily in scheme, though it could be... But in coaching.
Haslett at this point, even if the injuries are a huge factor, needs to be used as a scapegoat. Firing Shanahan is easier said than done. He'd need to really screw up to be fired, although he may have started the downhill slide thanks to his post game comments yesterday. But the 'Skins have a reputation of canning guys quickly. But change is obviously needed, so who needs to be the guy? How about the guy who has consistently been outperformed by his counterparts week in and week out? The guy who's track record speaks for itself? It's got to be Haslett.
Furthermore, you don't EVER just say, "hey, we need to go back to the 4-3!"
Changing it when we did and how we did was an error. We should have, if intent on changing, converted slowly with a hybrid system using both fronts until we gathered the proper personnel.
The answer in what to change is simple: The coordinator. You pick the guy who has vision, passion and a PLAN. Then, you let him execute it. Will you be able to go and get everyone he wants? No. It's simply not possible. But you give him free reign to do as he sees fit. Let him run the defense. I don't care what defense it is as long as he schemes intelligently due to personnel. It could be a 4-3, 3-4, 5-2, 46, 2-4, 4-2, 4-4. Quite frankly it doesn't make a lick of difference to me. I always laugh when people say, "Let's go to the 4-3!". You go to the system that works best for you. I'm not sure the 4-3 is the answer. I'm not sure the 3-4 is the answer. Right now, I think we're best suited to run a hybrid system. We don't have the pieces to run either one on a full time basis. Once we go shopping and see what's available we'll know what direction we need to go in. And any coordinator we bring in should be able to adapt to what we have if we don't get what we want. It goes back to the whole "plan" thing I was talking about.
For the record, that doesn't mean we don't let the coordinator transition to the defense he wants. He HAS to be given that freedom. But he needs to do it gradually if we can't get the pieces we need right away. And again, I don't mean all the pieces, just the ones that are necessary to reasonably run a specific defense.
Hire the guy that wants to succeed and is hungry.