Welcome to the forums! No other options, IMO;
Under 2006 IBC;
http://www.cmdgroup.com/building-codes/arizona/
WRB and flashing, as said above;
http://publicecodes.cyberregs.com/icod/ibc/2006f2/icod_ibc_2006f2_14_par010.htm
" 1405.15 Fiber cement siding.
Fiber cement siding complying with Section 1404.10 shall be permitted on exterior walls of Type I, II, III, IV and V construction for wind pressure resistance or wind speed exposures as indicated in the manufacturer’s compliance report and approved installation instructions. Where specified, the siding shall be installed over sheathing or materials listed in Section 2304.6 and shall be installed to
conform to the water-resistive barrier requirements in Section 1403. Siding and accessories
shall be installed in accordance with approved manufacturer’s instructions." Bold is mine, from;
http://publicecodes.cyberregs.com/icod/ibc/2006f2/icod_ibc_2006f2_14_par058.htm
From manufacturer; "27. Can LP® SmartSide® siding be fastened directly to the studs?
a. Certain LP SmartSide products can be attached to framed walls without sheathing such as Precision series siding. Refer to the LP SmartSide installation instructions for the specific type of LP SmartSide siding you are using. Note that a code-approved breathable
water-resistive barrier is required between the siding and the studs." from;
http://www.lpcorp.com/Resources/Lit...Sales_Sheets/LP_SmartSide_Trim___Siding_FAQs/ Bold, again, is mine.
The building paper/house wrap is the exterior water barrier after the siding, draining the wall- covering the stud/plate faces. An interior vapor retarder is recommended for your location, but not a true "vapor barrier" (Class 1) mirrors, foil wallpaper, etc. to stop exterior water vapor and condense in the stud cavity with the AC on;
http://www.buildingscience.com/documents/reports/rr-0410-vapor-barriers-and-wall-design
Kraft paper (asphalt) faced insulation batt is fine; Fig.#6;
http://web.ornl.gov/sci/roofs+walls/staff/papers/143.pdf
Gary