I agree with most of those, nothing cast iron, 80L of water, chainsaw, etc but yes to the snorkel with a sock filter and you'll need a gas bottle to cook with at breaky and or lunch, cant always build a fire. and agree with go as light as you can cause you'll end up heavy anyway,
I don't have heavy duty coil springs so adding airbags to help from the rear sagging, dual battery setup is good but only if you have a fridge freezer to look after, inverters can stay at home along with all there power draining mates, spares for your 4wd, research weak points of your vehicle and make up your mind on whats overkill, you've got under 6 months till you go, same as me, and it'll come up quick, it's a big trip and it does need alot of planning ahead like you already know, I'll be going up the creb, ott, frenchmans, palm and others but I won't be goin down gunshot Haha, Have a great trip Phill and might see ya up there, Cheers