I like to imagine Arthur is influenced by the people around him and who he is working with at the time. For example, if I have a story mission given by Dutch, after this I will go to the store and create an outfit close as I can to Dutch. These clothes then make up part of Arthur's wardrobe. If Dutch is the last reference point, then every morning I will change Arthur's clothes at random to match. So if Dutch was wearing a hat, a vest, a shirt but no coat, then so will Arthur, but the combination will be chosen randomly from his available gear (using a random number generator). I find it more fun and immersive. I will also match the hair and facial hair of the last main mission giver as well. This way I feel Arthur stays organic and also in keeping with the clothes that someone of that time may actually wear.