These bags are quite durable with roller blade wheels and have a basic pack suspension. I drug one down miles of city streets but I don't know how well they would work cross-country. Also note that they are very large for a backpack and might be difficult to carry if fully loaded.

http://www.mec.ca/Products/product_detail.jsp?PRODUCT%3C%3Eprd_id=845524442506335&FOLDER%3C%3Efolder_id=2534374302861417&bmUID=1220313490590

I am thinking that some adaptation of a golf trolley might work better over a variety of terrain and still be collapsable.