I think that if you have collectibles, once a child has collected one you should decrease the number of times it appears to make it a bit easier to find the others.
I like the idea about training children, but there is no reason to train all of them since all kids grow up and it would be a lost effort. There should be a special child that will appear at one point in time that tells you that he/she can be trained to do things.
I think that you should be able to build the fires, giving the builders more jobs and that there should be more then one, like having one fire per hut.
In VV3 I also think that there should be a way to have elderly people live longer.
I would also like it to be easier to train the healers. in my game the healers wouldn't stay at the plants, they would just wonder around.
I really liked the idea of a clothing hut, to use up all of those points you accumulate after your tech items are fully researched. maybe something else like that, sorry I really have no full ideas.
I would like it if you could increase the size of the island. Maybe once all of a kind of collectible is found the island gets bigger.
I think that if something like the gong is going to be made it should be some of the first things discovered, so that it can help the villagers at the beggining.
I don't think that it would be a bad thing to have some of the same puzzles from vv1 and vv2 in vv3 as long as you discover them in different ways.
Also, I liked the idea of a school in vv1 but if we could increase the childrens abilities before they become 14 after a certain point in the game, it would be really cool!!!