Except the unconventional response in this case doesn't address the question at all. The question was about cutting weight, and the response would cause a significant increase in weight. Also, if he's sweating so much that soaking outer garments is a serious concern then he's wearing too much stuff.
surprisingly it cut wait. As I got a benefit from using cotton, I can bring less clothes to stay warm. if you lost fifty percent of your isolation by damp clothes...you most have an other shirt to stay warm. T-shirt is less bulky to stuff in a pack sack and you can cut weight. Better night and less food have to be take in account.
Wearing too much means that you need space in your pack sack to stuff your clothes. But you can also loose heat by exposing the cotton t-shirt to the cold.
For multi layer, if you use four pile of a same tissue or one large of the same tissue, there is not a lot of different. If you use one tissue who act like a sponge, and other like isolation and other like skin protector against damp, a windbreaker, etc... you are more adaptable to any changing weather condition like the one that can happen on Mt Washington.
note; I agree that there is more trick about how to stay dry by wearing less clothes. Not many people know that the body take at least twenty minutes to react to cold weather. If at the beginning you wear less clothes, your body will produce warm for that temperature, and after you can pile more clothes to be comfortable. If you begin with a lot of clothes, at each times you will remove a piece, you are going to froze because your body will take and other twenty minutes to acclimate to the new environment.