To give an idea of what can be lost/changed, this is what Iv done:
Aircon
Power steering
ABS
Half sized rad
Engine mounts
Stainless exhaust and manifolds
Induction setup
Flyby wire throttle conversion
Light weight alloys
Coilovers
Carbon bonnet
Carbon spoiler
Seats and belts - swapped for buckets and harnesses
Interior plastics
Speakers and stereo
Spare wheel and tool kit
Sound proofing floors and behind dash
Sunvisors
Headliner
Rear wiper
3rd brake light
Electric sunroof - swapped to ali plate
Electric mirrors - swapped to manual
Excess wiring
Removable steering wheel
Admittedly mine is a weekend/track car, there is still more to lose like the glass windows, doors, tailgate etc
I might go the ITB route yet so can lose the inlet mani, induction setup aswell.
Just depends how far you want to go, the more you lose the less comfortable it gets!