Perhaps more variety in furniture? Maybe a stockpile sort of thing that can store more of a specific resource (I.e., it can ONLY store wood OR metal OR plastic, etc. but it stores more than a chest can hold). The other furniture that is almost a must have is lamps that can attach to pillars and not need to sit on the ground. Speaking of furniture, maybe the ability to sit in the chairs and perhaps fish while sitting? That would really fit the theme. :-)
Relating to the earlier topic of food variety and fruit trees, you could implement a 'deep pot' for things like fruit trees (it takes up more space, but you can plant a fruit tree in it). The fruit trees should also take MUCH longer to grow than the palm trees, but should also probably be regularly harvestable for fruit. (Suggested fruit: oranges, lemons, grapefruit).
Furthering the subject of food, you could introduce spoilage of cooked food (and the ability to prevent spoilage? Dehydration/salting for early-tier, canning for advanced?). I do also agree that there should be more than five kinds of things to eat :-P
For animals, I saw the idea for a fishtank earlier in the forum, perhaps be able to catch two live fish and let them breed for food? It would probably be something that's pretty advanced, requiring you to use the furnace to make glass panes or somesuch. It would also be semi-feasible to rescue a chicken at some point and have to build it a nest box (planks, nails, thatch) and feed it so it gives you eggs. (IRL layer chickens give about one per day during the up season and one every two or three days when the days are shorter). (Also IRL stuff about chickens: they are NOT herbivores. Seriously, they'll try and often succeed eating anything. Feeding them fish is entirely feasible. IRL nest boxes do need their straw, or in the game's case thatch, changed out regularly.) This kind of thing could also be applied to pigeons, which are prooooobably more likely to be encountered on the open ocean. ;-)
Dolphins would be cool, though impractical, I imagine. /shrug
A daily/bidaily autosave would be nice.