1993gsxr903 has good point, especially on tires. Being a possible large weight savings we need to know how light you can go before having to replace tubes/tires way too often.
For wheels, Stan's is
www.notubes.com. There is a wheel builder/weight calculator on the website that is super handy. Just by changing the rim can save you 200 grams total which is nearly 1/2lbs (of rotating mass also). As mentioned tires can save you another ~400gr so you've just saved 600gr of rotating mass!!! By going tubeless you can save more.
For Stan's, Flows are going to be your choice if you are heavy or ride technical stuff with drops/jumps. If not, then go with something like the Crest or Alpine.
Carbon rims are expensive and as one other said, you would be better off starting with a lighter bike if you want to dump that much into it.
What I have done on my Epic is have 2 wheelsets, one for my typical rides (Stan's Flows) and then another lighter set (Stan's Crest with lighter spokes than the Flows) and only use the Crest for racing.
But, like mentioned, if you ride in the southwest desert you absolutely can not go ultra light weight on things like tires. Schwalbe and Continental are 2 populare tire companies that are weight conscious. WTB is typically not weight conscious. There are TONS of threads on tires/wheels in that forum too.
You mentioned your "cockpit" is setup for you and you don't want to change anything. It's not that hard to simply replace what you have without disrupting your setup and still drop lots of weight. Some simple measurements can replace your seat where it was, and if you like your stem length/angle just replace with the exact size but with a lighter piece, voila! This area it wouldn't suprise me if you could loose 200gr.
? - Do you know which model of the WTB Laser V you have? The lightest is 240gr while the heaviest is 290gr. A sub 200gr can still be comfy for most and won't cost a fortune. Get measured for you correct width and let us know so we can recommend a seat for you.
As mentioned what cassette do you have now? If it's an SLX or cheaper SRAM go buy a XT or look for a XTR online on sale, this could be 100gr easily without costing you too much. If you are on a budget just go with the XT, the extra weight savings of the XTR is not worth it IMO.
As an owner of a 6in AM bike, I like to think there is a nice compromise on weight vs durability. My Enduro weights right at 30lbs with fairly heavy UST tires. I can drop a full pound by going with lighter non UST tires for my midwest riding, but other than that I don't want to dump money into it to have a 26lbs AM bike. I bought a used Epic for that!!!
