Maybe an option to remove some trees from the island would help for example loggers who would delete hardwood trees and pinewood trees in a certain radius of maybe 12x12 around the camp placed may allow some space to be created on the islands.

Possible maneuver to get other islands...

Build a Dockyard to make ships, these ships may or may not find small cluster of islands of 2 or 3 spaces which may or may not contain resources, upgrading these ships will be done via the dockyard, to do this you will need to upgrade the dockyard, upgraded ships have the same potentiality to find bigger islands to use, these islands can of course be looted via PvP if the gods decide to allow it or not.

just a thought on maybe a few ways to get more space on the island and more islands to look after