Also sounds like something Ted Kaczynski would've been interested in using back in the day. It has all of the elements of a literal bomb delivery service: operates outside of the mail security apparatus, probably built on a shoestring budget so no background checks for the senders.

The conclusion would probably be that the supply side would need to be trained and certified as courier operators.

Are the legal liabilities way more serious than those that Uber faced? To be fair, Uber founder faced a lot of legal issues and stress.