Check-in explicitly asks you "have you packed your bags yourself", and then you have to either say "no I have this random package from a stranger which might contain anything" or lie to customs.

TBH, I can't really think of a market for this that isn't contraband. The "last mile" looks really annoying as well.

Edit: I think it's a legit marketing question for OP. Name three different kinds of item someone might want to use this service for.

I'll even give you one: there's already a small cottage industry of reshipping companies from e.g. Japan, who will let you buy stuff from companies that won't themselves do international shipping. Ship to re-shipper, who then handles the international part.

You might be able to get a market started if your model starts with only items bought from legitimate retailers. Effectively a really long distance doordash.