QDM
The Freedom Trail is/was one of the more severe routes, certainly not one to be attempted lightly and probably safest with a guide. OTOH further West there are several relatively "easy" trails that run out of a spot called Hospice de France, near Bagneres de Luchon. To give you idea of the difficulty I did the "top" one of these a few weeks back with a 7 year old in tow. Unfortunately my guess is the easy routes were also the ones easily policed by the occupying forces. Certainly in Winter any of these routes would be impassible or nearly so. Contrary to the opinions of some Alpine buffs the Pyrennees are proper mountains, there is still snow in gullies in July, plus permanent glaciers around the high peaks..add that to elevations in excess of 2000 metres and I think you are right in saying that the physical state of many of the escapees added significantly to their problems.
If I could get the hang of posting pictures here I would post the piccies I took of the memorial to the escape lines that is at Hospice de France..in the meantime good luck.