Do any of the symbols that you suggest signify "olive" here?
I guess if one digs deep and wide enough, one can find something to prop up any prophecy.
Sometimes understanding what a prophecy means isn't immediately evident. Sounds like you don't have a high regard for prophecy in general, but I will note that the prophecy we are discussing is extra-Biblical.
My reading of St. Malachy's prophecy on a a Roman Catholic web site didn't have explanations for all of the Popes, either.
What is interesting is that according to the prophecy, Benedict XVI is the second to last Pope.
As far as Malachy's prophecy I take it with a grain of salt and prefer to focus on the clear as opposed to the unclear. "Seek first the Kingdom of God" - Jesus