As a Redskins fan, I kind of have the same position I do with Hewitt and Mason. Although I'm not thrilled with what either one has accomplished, I'd rather roll with the devil I know next season rather than scrapping everything and starting over.
Washington has been horrible this year, but there are a lot of factors that go into that, including a ridiculous amount of turnovers (not on the coach), injures (RG3 was never really himself), some poor management decisions — which is obviously on Shanahan as the GM — and the salary cap restrictions (which is on Snyder and Allen).
That said, Shanahan like Hewitt needs to shake things up with his staff if he stays around, and I would start with replacing special teams coach Keith Burns. He also needs to be wise in free agency — like bringing in good players rather than big-name players —to fill some holes on the offensive line and the secondary since we don't have our top draft pick. I also wouldn't be opposed to a trade or two if that upgrades us, and yes that includes Cousins.
I am admittedly loyal to a fault as a fan, which is why I defend Hewitt and Shanahan. Replacing both might be the answer somewhere down the line, but I think both deserve at least another year to right the ship. If things don't get better — and there's no given either team will — then they both have no choice but to bring in replacements and start anew.