It never get "that" hot inside of the airplane. Come on.
I didn't have jacket or even sweatshirt because I was flying between two South American hot countries. In each place temperature was around 90 degrees. The cabin was about 65 + I was seating in emergency exit row.
I had two blankets. One on my upper body and one on my legs. Had hot tea and I was still cold.
When you fly in warm cabin you can remove layers and be comfortable in the t-shirt. Also you can have cold drink. It will cool you faster than hot drink will warm you up. Also in most airplanes you have personal vent with cold air.
You don't have to smell people around you. When I'm flying with smelly person in my vicinity I put the vent straight on my nose and I'm good to go.