That seems fair, and I liked the part of the having spent the last 10 years of his/her life in the US. I still believe, though, that a fraction of the person's first 10-20 years should be in spent in the US as well. This could get complicated, but it may work to require that the person have spent 75% of their childhood and 75% of the last 10 years in the USA, and possibly 50% of the time in between as well.