One example: post couriers are not responsible for the contents of the envelopes, thats why they can work with very low salaries, but more or less worldwide. Smuggling of narcotics is other thing and it is (rightly IMO) prosecuted. Having a contract of delivery of some yacht you are always risking that you don’t know what is inside and if stopped and found something prohibited - full crew is liable as you cannot prove the contents are not yours. Thats why such contracts are not very cheap and usually working within web of trust which includes clients.
If building such delivery network - the question of responsibility of the couriers for the contents of the package is the first one to address; without resolving it, it will always be an expensive smuggling alternative, not a working network.