Personally, I figure you could make a pretty decent camel-archer out of the Saba archer-spearmen just by giving the model the appropriate "mounted" skeleton definitions (ie. like generals have). Pretty much the exact same guys, just atop a smelly, ornery herbivore after all. You'd still need to spend a slot on the camel of course - I figure the rather redunant one for the Yubtseb oliphants would do fine... or is that needed for something ?