I suggest that you avoid the use of aluminum alloy nipples. Use good quality brass ones instead; they are stronger and less prone to corrosion which can lead to seizing or failure; the weight penalty is minimal. Carry spare spokes (you will likely have 3 different lengths) and nipples on your tour. A Fiberfix repair kit may be useful especially for temporary repair of a broken drive side rear spoke until cassette removal can be done. Alternatively the Stein mini lockring tool http://www.jastein.com/Html/Tools_for_Wheels.htm can be used for the job