Welllll, you start with, honey what would you think if WE (notice I stress WE, they want to be part of the decision making) rearranged a few things and turned part of this room into a sewing area for me. Blah blah blah. Go on to explain the benefits of this for you, so you are not cramped, sewing in a closet. If he is thinking ahead to when you move to a retirement home, why can't he make concessions now for that same reason now.
Just a thought. :D :D :D :D :D
Good luck. I hope this works out for you.