Dieting cars is my specialty with keeping the car looking stock! Here are my ideas that would get some serious weight loss going without removing seats and all that stuff.
1. Remove all sound deadening material under dashboard and floor of car. Right there I gurantee that you will get out at least 30 lbs of unused weight. On a 2000 Civic SI Sport Compact Car took out 65 lbs of sound deadening material. Might be a little bit louder but will look stock.
2. Carbon fiber hood. Check out Fiber Images or contact Carbon by Design and see if they are going to make one for your car. Also switch out the rear trunk for a CF one while your at it. CF is also paintable, but that checkered gloss black CF is as sexy as a 5ft 8 blonde in heels.
3. Jack as mentioned above and spare tire.
4. You have a great sound system in your car, but if you are really looking to lose weight, yank the system and all components. Mostly yank the amp and the built in subwoofer. That has to be at least 20lbs right there.
I bet if you took a close look at your car, you could lose 50 lbs in no time. hope this helps some.