As hard as it might be i love most of the ideas, but the one about having endless expansion is the best i think. People could submit their own islands with little puzzles pick from a large list of events and submit their own parts of the island on the forum for others to download and try. As far as charging for each new piece i dunno about that maybe official large releases that offer a lot more than user submitted ones sure, but once the game is purchased at least make them cheaper. 3$ expansions for official and free user submitted ones we could rate at how good they are. Perhaps release an editor where we could place the buildings where we want them to be built or pick the buildings, how much a crop will produce, how many berries a tree has, etc, and i think this would make the game about endless. As well as making the game more appealing to people who beat it, the ability to play others maps, and make it so it never gets boring or never is a lack of something to do.

My 10 cents. Love the idea of animals running around, maybe a bear attack wounds a villager, or Lassie saves a kid from a snake or something. Neat things like that make the game more enjoyable (not that its not now by any means, i still laugh at some of the behaviors i never saw before)