More manufacturers.
Most builders in the "large 4x4 expensive" league vill accomodate your every wish. This means to build on a vehicle/chassis of your choosing (you can even deliver it yourself), build a cabin to your wishes (exterior/interior dimensions), including embellishments like rounded corners, over-cab alcoves, etc. etc.
Interiors are almost always fully customisable both in layout, choice of materials, etc. The technical side is "the more you pay the more gadgets you get."
Some producers have very poor web presentations (websites), but are still very good builders. Find one to suit your budget.
Make some choices before calling around:
*Should the cabin be made with an outer skin of Glass fibre or Metal? (As most builders only use the one or the other).
*Is it to be built on a light 3,5-7,5 ton chassis, or a heavy 7,5-UP ton chassis?
*Do you want a new engine/chassis with Adblue (urea), or find a lightly used (EURO3) class chassis without for use in remote areas?
*What is the minimum amount of liquids you want to carry (a common scenario is about 400-600 litres of diesel, 300-600 litres of water, etc.)? This will affect the chassis type you can choose, as 1 ton of liquids adds a lot to the gross vehicle weight.
*The gross vehicle weight and outer dimensions of your vehicle will determine what roads you can travel (at least in europe). If you want to get around mostly everywhere, go for a vehicle below 7,5 tonnes, and maximum 3,45 metres height. (This is a major constraint on chassis choice and vehicle size.)
Lots of good manufacturers mentioned, but see also:
Tartaruga:
http://www.tartaruga.ch/stage/expe/index_expe.shtml
Exploryx:
http://www.exploryx.de
Bocklet:
http://www.bocklet.eu
Orangework:
http://www.orangework.de
Ormocar:
http://www.ormocar.de
And many, many more...
Personally, in the "cost no object" category I would look at Unicat and Action Mobil, in the mid area Bocklet, Exploryx and Ormocar would be my contenders, and in the more affordable end (and what I finally ended up with) you have Bimobil.
