Yes, if the Catholic Church were not so darned ... Catholic ... we could join the LDS and the Anglicans in changing dogma on the fly.

Some minor notes ... the "committee discussing birth control" was not granted any authority to approve or disapprove anything. It was supposed to be giving the Holy Father some pros and cons to consider. And its report was not for public consumption, but was "leaked".

When we talk about "chance", we mean if something is certain the probability is "1", and if absolutely positively cannot occur the probability is "0".

When you write "During Vatican II the chance existed to change this ..." we're looking at 0.