Why can't larger ships be unloaded onto smaller ships at sea? Then those smaller ships would have access to a wider net of ports. Like a river flooding out across a delta before it reaches the ocean, but in reverse.
only the very tiniest of container ships have their own cranes onboard, anything above the tiniest size is entirely dependent on shore handling cranes.
also moving cargo between two ships floating around at sea is dangerous and difficult, giant ships are not meant to hold position parallel to each other in the open ocean (or indeed closely parallel to anything) without the assist of many tugs.
a "geared" (with crane) container ship looks like this, and even so it would be a very risky move to use the crane to do anything other than load a container to/from a wharf while the ship was firmly moored to it.
The closest thing to this which has been tried was the LASH (Lighter Aboard Ship) system, where cargo was loaded onto unpowered barges that were in turn loaded on board a specially designed ocean-going ship. The barges could be unloaded more quickly than break-bulk cargo, and could be towed on inland waterways.
This proved not to be able to compete with container ships when they were introduced. The last LASH ships in regular commercial service AFAIK were the Baco-Liners, which served small ports in West Africa and were scrapped in the early 2010s.
They actually still do this in Hong Kong, but not much, and it's unheard-of elsewhere due to the size of the cranes needed, most ships not having their own cranes, and safety concerns.
There was a similar system, which got more or less replaced by standardised containers - the LASH carrier fleet took freight in standardised barges called “lighters” which could be floated out at ports, but couldn’t really compete with the multi-modal train-to-ship-to-truck container platform.
also moving cargo between two ships floating around at sea is dangerous and difficult, giant ships are not meant to hold position parallel to each other in the open ocean (or indeed closely parallel to anything) without the assist of many tugs.
a "geared" (with crane) container ship looks like this, and even so it would be a very risky move to use the crane to do anything other than load a container to/from a wharf while the ship was firmly moored to it.
https://www.google.com/search?q=geared+container+ship&client...