Possible, but unloading cargo would be more involved. Also, without access to electronic manifests, I am not sure there's any easy way to know what's in a container, not to mention many of them would be stacked in such a way as to inaccessible. All of which is a lot harder than ransoming a crew. I suppose it might be possible for pirates just to threaten to sink the ship.

One would simply disable propulsion and communications, and then haul the ship elsewhere for classification and sale of its cargo.

With no humans on board, then there is no incentive not to use deadly force for disabling critical subsystems.

equivalently, there's no real incentive to not use deadly force to clean the ships of pirates as a deterrence and take the write off on any damages.

I suspect with drone ships and the lack of crew liability, there will arise contract security companies with pre-positioned ex-seal teams in hotspots to deal with piracy.

With access to electronic manifests, you could program the logistical system to deliver the goods to the destination of your choosing. Which might be easier than piracy.

Another thing are systems like the one done by ATG - planning better routes for ships with multi-agent models. For example the paper Vaněk, Ondřej, Ondřej Hrstka, and Michal Pěchouček. "Improving group transit schemes to minimize negative effects of maritime piracy." IEEE Transactions on Intelligent Transportation Systems 15.3 (2014): 1101-1112.