With all the doors and windows, I think you're unlikely to be able to get both a mud room and a pleasant sitting room out of the space in here, so decide which is more important. You could easily convert the current bench wall into a closet wall, either as open cubbies or as closed storage with bins and hanging zones.
That might be your best bet, and maybe the single chair at the end with a proper reading lamp can be an occasional perch while passing through. But probably you'd sit outside, weather permitting...
Q