I admit that I haven't read every post on this thread so I may overlap a bit.

Here are my thoughts:

-Rain. They do a rain dance, why doesn't it ever rain? They could go inside when it does.

-Lightning once in a while with a big storm. This could also generate fire for cooking if the villagers had a certain tech level and then they could also gather wood to keep it going and do cooking.

-Seems like something ought to happen once in a while after someone swims in the lagoon aside from the GC and the special fish. Maybe it increases their skills in something or adds a year to their life or something? It is magically clear water after all.

-The GC should visit the idol and temple and do something there once in a while. Dunno what, but it seems to fit.

-There should be some jealousy over mates. Perhaps if a male or female tries to mate with someone right after mating with someone else there could be some pushing and shoving going on.

-Should be some holidays. Perhaps even just expand the reason behind the GC parties. Honoring the dead, worshiping the idol or temple, harvest feast...

-A monkey should wander out from time to time. There is text about monkeys but you don't see any.

-After all the puzzles are completed, there could be a reason for advanced tech points. For example, they could develop a wheel, dig a canal from the lagoon to the field for watering (which could make those crops really take off), build a boat to go off to the next island and start a new game, explore the cave...

- Something could happen around the treasure. Invaders? Decorate the idol or temple with it? Use it as a magnifying glass to make fire?

-Parents should teach their children to forage at the berry bush. When they're young they would only take one berry and eat it or whatever.

-A hut could be converted into a hospital.

Just some thoughts!
Tess