I think its perfectly possible to do this route at this time of year, although, if there's proper winter conditons, it might be hard doing it in the time. Inevitably, if you're going to take 10-ish hours, some walking would need probably need to be in the dark. A pre-dawn start should sort this out, though.
I think Wainwright's worries probably centre around limestone country under deep snow - ie the technical possibility of falling throught he snow into a pothole or a clint (or is it gryke?) As far as I'm aware, the only time something similar happened was a walker on Cross Fell who fell through snow down a mineshaft a few years back. Under normal conditions, this is probably a bit unlikely.