after 3 months in the field without proper resupply you're lucky to have soldiers look well-dressed, though they should be identifiable. After 6 months, they would mostly look like crap. Remember General Bonaparte's comments to his army on taking command in 1796? Those men had also been very poorly supplied, though they had also received a signifcant number of reinforcements and were closer to potential supply sources. The Army of Italy was not particularly poorly dressed. I reckon your Westphalians would have looked even worse. As a final consideration, reflect on their morale by 1813. What was the motivation to be at all soldierly, except for the few that liked it?
For modern evidence, look at WWII units in the Pacific for several months, Japanes units by the end of the war, Allied prisoners at the end of the war, and so on, to get an idea of how ragged and patchwork things would be.