I wonder if this chair is too valuable to modify the cushions?

I inherited from my mother this “Morris chair,” which she inherited from her father. My grandfather either purchased the chair around 1910-1930, or perhaps he got it from his parents. I love the chair, but the cushions are quite firmly stuffed, and I would enjoy sitting in the chair if the cushions were softer and more comfortable. My mother always told me never to alter the chair, identifying it as a very valuable antique. Looking at it, I don’t think the material on the seats is actually leather, so it may not even be original upholstery (if it has been reupholstered, it would have been before 1950). I don’t want to ruin a valuable antique, but I would like to make it a chair that I would enjoy using. Would reupholstering the cushions ruin the value of the chair? My grandfather lived in Ann Arbor, Michigan, but his family was from Chicago. Any information on the probable value of the chair would be appreciated.