>Even if you find a solution, you will be breeding resentment due to imposed inequality. Now you are facing a protest and political movement composed of immigrants and their citizen sympathizers who are demanding the ever-popular "justice, equality, etc". For a recent example see the illegal immigrant Debate in the US. Southern illegals are already entering the US (illegally) as if the borders are open, already face discrimination and restricted rights and already have a political movement to fight for things that matter to them.

Worst case I see is something like France, (and I'm picking on France, but my understanding is that this is super common. Japan and much of Europe also have a 'blood' component to citizenship.) where they don't have 'by right of the soil' citizenship; you can be born in France, but still not be a french citizen, because of who your parents were. And yeah, they see problems from it. They have a permanent underclass of hereditary non-citizens.

Personally, I think that as long as we keep that particular Americanism (which is to say, if you are born on US soil, you are a full American, and at least legally equal to any other American, regardless of who your parents were or what you look like, or what hoops you choose to jump through.) I think we'll be ahead of the game (vs. other countries)

"keyhole solutions" I think are feasible if they aren't multi-generational. You /really/ don't want to grow that multi-generational non-citizen underclass. If you only have those restrictions on people who immigrate, and not their children born here? I would see that as an expanded guest worker type program, and it would probably have similar political consequences as an expanded guest worker type program.