Again, experience says not.
"Your biometric database record would NOT be your identity -- it would only establish whether you are a citizen or non-citizen. "
I don't think you understand your own statement. If you are not a citizen then your identity doesn't matter. You don't matter if you are not a citizen so who cares who you are. Not a citizen? No vote, no credit, not driver's license, etc.
"That's why there needs to be a system of back-up databases at the state level."
You obviously understand little about databases and government corruption.
What country are you living in?!?! First of all, there is no connection between citizenship status and credit or driver's licenses -- not legally, and not in practice. As for voting, I hate to break it to you, but as it stands now, plenty of non-citizens are voting. How easy is this? So easy that a non-citizen can end up registered to vote without even trying, thanks to "moter-voter" and various other schemes to make it easier for apathetic and non-functional people to register to vote. Last year, a foreign student at my alma mater (in Pennsylvania) was startled to receive a voter registration card in her school mail box. Since she wasn't interested in casting a fraudulent vote she looked into how this could have happened. Turned out that some of the folks handing out driver's licenses are so eager to get everyone registered to vote that they register even people who decline the registration option. And needless to say, no one anywhere along the line cared to inquire or verify whether this young lady -- or anybody else they were registering -- was a citizen.
Thanks for pointing out another positive aspect of my scheme. Although undoubtedly a few legitimate citizens would run into database glitches preventing them them from voting in one election, this would be more than compensated for by tripping up all the illegal non-citizen voters who currently dilute the votes of citizens.