Beg to differ, but this situation is unprecedented in our history. We have to look to how our traditional law functions in similar instances to determine how to proceed if he's found to have committed actual fraud against us.
In any similar instance, I don't believe that any court would find that because a person was elected and sworn in, that that somehow mitigates the fact that they were never entitled to the office to begin with. There is no retroactive immunity from logic and reason in this regard, in my personal opinion.
Only a qualified President can be impeached, per the Constitution. If Obama is proven to be unqualified, and therefore ineligible to hold the office of President, then it just does not follow that he must be impeached. Logically, and legally, I don't believe he can be, as he was never the President to begin with (even though that fact is discovered after the election and swearing in).
Again, I believe that we have to look to how any other fraud of this type would be prosecuted, to divine the answer.
You are right. The Constitutional qualifications are precise and fixed. No swearing in ceremony can obviate them. If a swearing in ceremony meant that the Constitution could be violated every moment of every day by the swearee, the the President would be placed above the Constitution, and I can tell you that he is NOT. He is subservient to it.
If an individual is not qualified under the Constitution then he CANNOT be President. Ever. At all. And that means that Obama would not have to be removed for the Presidency, as he would NEVER HAVE BEEN PRESIDENT AT ANY TIME. All his acts would be void.