I have thought of this idea before and my thinking was the same of finding protection and risking getting ganked along the way. It's a great idea and I think the homesteaders would really like a service like this. Even bigger tribes could use your services. (You know at Christmas time even FedEx gets more help) =)

Making good relations with homesteads and tribes throughout Xsyon will help you get across to make deliveries. Like someone else stated the Pony Express idea.

Think you're on to something and should think out and tweak ideas. This could be something really good.