Village Sim is the best of the bunch.

The question I have, why not start a game line rather than have them one-offs? For example, Village Sim suggests a huge potential for expansion ideas. More puzzles, more villagers, more things to do. I don't know your financials but it stands to reason that the risk and capital involed in creating a Sim expansion would be less than developing a whole new game line. Not to say ignore the idea of new games, just that if you have one or two ideas that suggest evolutionary continuations then you could mantain those lines while developing entirely new games. I'm not thinking of sellout overkill, just a nice progression.

Another possible idea, integrate fan-based mods into official expansions. Release the dev tools so they can create new villager graphics, new scripted events, etc. Users can submit mods to LDW and the winners are included in official updates to the game. New content is created and interest in the game is sustained with a minimum of additional investment by LDW. Most of the playtesting would probably be accomplished by the fan community.