Any crossing 'viable' if it works... but 'ethical'? a different matter...
I've covered this in the Osmotherl(e)y CP recce thread (page14) and give detailed notes on my choice of route.
Ronald covered the route in 5 days whilst taking notes for his own guide book - hence the 'trot and linger'. He suggests some interesting alternatives which could be seen as improvements to AW's original route as I'm sure when Wainwright devised the route he had overnight accommodation and access in mind - Grasmere for one and maybe the dog leg nearer to Osmotherley. Certainly for me last year (though not among Ronald's suggestions) the footpath
after Scarth Nick was handy in getting me to a meal and a route that I would choose in future, though a little work is needed on waymarking the path through the woods after the forestry track is reached... this must fall in SC's territory?! This to me represents an improvement to the original line as the path is delightful - dropping steeply as it does through deciduous ancient woodland. This, of course avoids the summit of Beacon Hill (and the Radio Station) and the wide land rover track down into Ingleby
Even though 'approved', for me a low-level Swale route missing out Gunnerside would be unethical as would skirting Nine Standards of course, but why Mill Bridge if you don't need the youth hostel or Grasmere or the Traveller's Rest - likewise Loft Beck if the weather's good and you don't need Black Sail when you can include the man's last resting place?
I suppose a good rule of thumb is don't use a road where you can use a green road; don't use a green road where you can use a bridle; don't use a bridle where you can use a footpath.