More structures that can be interacted with i.e cooking stations that can combined foods with spices etc that are grown to create food that fills more hunger? Stations to create more tools/weapons for defending raft? More equipment for fishing?
Raft upgrades? Upgrade the raft from wood to stronger materials for shark attacks.
Lights?
Day/Night cycles? implement beds to speed up cycles.
Decoration blocks to spruce up buildings created on the raft?