What type of package is small enough to fit in someone's luggage, light enough to not cost extra baggage allowance, tolerates non-delivery well enough to lose 10% of shipments to flaking non-professional couriers, and is not well-served by UPS, FedEx, or airmail, and cannot be transported at rock-bottom costs with mild latency via a shipping container?
I have an answer to this question: illegal drugs. I don't have a second answer to this question. This makes me think that you'd have difficulty finding 1,000 of legal packages to run through a proof of concept, to say nothing of scaling to the millions you need to have a viable logistics business.