I think the Giants have twice given Coughlin one-year extensions before granting longer ones.
Given the circumstances (mainly the salary cap penalty), give Shanny a one-year extension thru 2015 (so he's not a lame duck in 2014) and have next season be "put up or shut up" for him. And if we don't have a winning record then, Snyder can decide whether to cut ties and only be on the hook to pay what would've been Mike's 2015 salary.