Well i must say that the idea is presented in such manner that leave more questions, which can be good as it sparks interest, but it is also so confusing, that i am really having hard time imagining how it will play.
The theme is excellent and you sound like you have the technical means in supporting it, but it all comes down to what the player will be able to do in the world and what challenges they will face (and i must say that from reading the title alone, you have got my imagination rolling, while the introduction left me with a big question mark).
Will the NPC face some sort of danger? be it from starving, falling down because the rig got broken for some reason or any other non combative manner.
The notional game, is to build the rig up from a relative skelton into a thriving community. So the "risk" I guess, is that you fail to build the rig in a way that invites NPC's. I'm kind of thinking along the lines of Harvest Moon and SimCity here. In that some aspects of the player-NPC-rig relationship are about personal attachments, while others are purely functional, like "does an NPC have somewhere to sleep". Fulfilling the needs of the NPC in terms of fundamental needs and social needs are what I mean when I say its "sims like".
The challenge is more of a construction one, but with social elements in it. So can you build a rig that encourages trade income, but balances it with social function (an example would be can you build a system of trade that doesn't lower the living standards of the people on the rig?).
Its kind of hard because I can't point to a single example of a game like this. But only to examples of features from other games. So it sounds like I'm being too ambitious and trying to make all of them, when in reality I'm simply picking aspects or mechanics I like from other games and trying to experiment with them.
My main way of approaching this is to try and think of what I would want a community to feel like if I were in charge. What would that be like. Then layer on a fantasy setting that has different laws of physics etc.