Ruthless eh?
Nitrogen in the tyres, air out.
Weigh wheels change to steel if alloys are lighter, or vice versa.
Spare wheel, out it goes, along with the jack and tools.
Run on bald tyres, tread weighs kgs.
Balance weights (if any) remove.
Keep oils and coolant at minimum levels.
Any radio, or headset dedicated satnav.etc, out, you can get everything via internet on the phone.
As for books? well enough said.
Carry only as much fuel as strictly necessary, phone will show fuel stations at destination.
Carry no water, with a bit of planning bound to be a supermarket source at journeys end,
might as well remove the water tank itself.
Grey water tank, out that goes, hose or basin (bean can better) straight out on wherever.
Leisure
battery, obviously out, the starter will be more than enough.
Pots and pans.... sling out. Buy as much canned grub as possible, you can heat beans and the like in the
opened can. Dehydrated food when you fancy a slap up feed, but only after a can or 2 becomes available.
Toaster, ridiculous item, bread can be toasted over stove stuck on the end of a lightweight aluminium camping fork.
Kettle? What's wrong with an empty bean can.
Cups, yep the old bean can does it.
Fridge, out it goes. With canned food only carried, it's entirely unnecessary.
Could go on with suggesting more weight saving tips, but I have an idea they won't be appreciated!