Help me build my Bike long distance desert bike

Hey guys,

I would really appreciate your help with this as my knowledge of bike components has become very sketchy over the last number of years.

I used to be really into cross country in my teens riding trails nearly everyday but havent cycled much for some years now. My interest was sparked again recently on a trip to latin america where i rode some cool trails. Now me and my friend are planning a bit of a longer trip in desert conditions (sand , rocks etc)

So basically i need a sturdy bike that is as light as a feather and can float on sand.

My starting point is the Surly Pugsley frame and forks. I need to decide on pretty much everything else. Here are just some of my erratic thoughts so far....

So i will obviously need wheels and big ones. I guess it will have to be a trade of from best in sand to best on rocky ground probably leaning more to working in sand (Endomorphs obvious choice??). I will also want a second pair of wheels for commuting about town that can be quickly swapped around.

Now as this is going to be a multi week expedition gearing ratio's and cranks etc are going to be very important. I do expect to be going over some up hill sandy sections.

Brakes will have to work in extreme heat and in sandy condition so I guess that rules out V brakes in favour of heavier disc brakes??

I will also need panniers front and back possibly even a trailer attachment.

Now i know there are a lot more things to think about including my budget but lets start with dream bike where no expense is to be spared. Just to say again i will really need it to be light.

Thanks guys