Build in some additional skills that only appear after certain puzzles/tasks have been completed and/or levels achieved, but are needed to complete later puzzles. For example:
- Once you've advanced to Level 2 Spirituality, you can now start training Shaman's, who lead services for honoring the dead, hold naming ceremony's for the 2-year-olds and Rite of Passage ceremony's for the 14-year-olds, lead island holiday celebrations (one of the island events I've had was commemorating their arrival on the island), etc. Then you have to have both a male and female Master Shaman in order to restore the ruins. Now the shamans can also hold ceremonies in the newly restored temple (perhaps calling everybody to the temple by blowing on conch shell) [and it would now be the shamans-in-training doing the task of "honoring the temple", which would give that activity some meaning, as it would be one way to increase their skills]. Then you would have to have a High Priest & High Priestess in order to chisel the icon!
- Once you've built the schoolhouse, "teacher" should become a new skill. Maybe incorporating the ideas above, such as they can't become a trainee teacher until they're a master in another skill; I like that idea. But then, of course, you have to tie that into achieving something else. Maybe, instead of the kids being born with a skill once the schoolhouse is built, they don't get that until you have a teacher and hold classes by masters of the basic skills. And classes would have to last longer than a few seconds! BTW, if the adults can go inside the hut for privacy, can't the kids go inside the school instead of standing around outside?
- Musicians! In the later stages of the game (everything at at least Level 2, and a couple things at Level 3, like construction and spirituality) it would be neat to have musician appear as a new skill, so the villagers can have music.
- Once you've solved all the puzzles, the villagers should be able to go explore more of Isola, or even neighboring islands, which would need more skills: Explorer, Sailor/Boat Builder, etc.