Docking rights for couriers have been an issue since Citadels were first introduced. The suggestion with the most traction was to let them deliver from tether.
CCP doesn’t seem to be in any rush to fix this and, since scams are perfectly legitimate gameplay in Eve, they may not believe it needs fixing. You accept contracts to player owned structures at your own risk.
It’s not obvious how asset safety would work in this context. The courier contract is going to fail if it can’t be delivered and, if the client actually wants the goods, you can setup an item exchange contract at a nearby station.