I agree, and if I had been one of the early fathers sitting down for the first time to discuss centering our whole doctrinal base on MT 16:18, I think I would have said, alright fellows, we need more then this one scripture, since it can be translated several ways, we need at least one or two more scripture to back this up.
You say this because you operate under the false premise that the Church comes from the Bible when the fact of the matter is its the other way around.
Why would Peter and Paul be adressing letters to the Church if it didn't exist. And besides, when they wrote their their letters it couldn't have been part of any NT canon the early Church had. It would be another 350 years before the canon was closed.
And if you were one of the early fathers... what would you say about being "born again"? Another single verse with two solid translations (even in the KJV) upon which whole doctrines have been centered.