I would rather have a bigger bag than not have enough clothes to stay warm.
If you can't find the fleece hoody you are looking for maybe you could add a small stuff sack full of cold weather clothes to your BOB.
(I am a bit like Art_in_FL with huge duffel bags.
But it was -42 here last Saturday so my Helly Hansen skidoo suit is in a duffel bag in the trunk of my car until spring happens. At least If I get stuck out on the highway I will not freeze to death before help arrives.)

One thing about a sack of bulky clothes is that it can get jammed into odd shaped spaces, used as cushioning for other containers and can have quite a bit of other stuff packed into it
8lbs is still 8lbs no matter how tight you squeeze it, or how loose you leave it.