In Factorio design this is simply increasing the buffer size. If the truck-loadings-per-hour don't increase then it's not going to matter how large you make the buffer. Adding a secondary site for putting containers also seems like it's going to be a new challenge for the logistics company scheduling the rides (I have a friend who deals with train cargo scheduling). Truckers who are used to showing up at the port are…
Providing that storage space will allow the trucks to complete their circuit.