Making a Pattern from Existing Clothing

I have several worn out jackets hanging in my closet that I absolutely love and want to recreate. I am an advanced sewer but am wondering how difficult this would be to recreate a pattern from them without tearing them apart. Does anyone have any suggestions about doing the sleeves and collars? That is where I see I may have difficulty in getting them to tailor smoothly. My thoughts were to piece butcher paper together and sketch the sections, adding seam allowance. Any help and suggestions would be appreciated. Grace