Actually, Cephas is just a different way to spell Kefas with the English alphabet.
John 1:42
And he brought him to Jesus. And when Jesus beheld him, he said, Thou art Simon the son of Jona: thou shalt be called Cephas, which is by interpretation, A stone.
It is evident that even at that time the name meant stone or rock which in English is interpreted as Peter.
And it makes no difference if it means a small stone or a big one, that is only a play on words.
It appears to me that Peter did take the lead among the Apostles which was known by Jesus that he would.
At the same time i do not see any where that it says any thing about Peter being Pope.
The Papacy is religion and i can not see Jesus as thinking kindly toward religion.
http://www.freerepublic.com/focus/religion/3562022/posts?page=204#204 (click here)
Check it out. Actually, Peter tried to impose himself as a/the leader of the Twelve, but in all, that never worked out very well. There were much better and more spiritual men who came to the fore, though Simon is respected for being one of the twelve; one used by Jesus to show that He can make a contributor to the Christian culture out of even the most unlikely individuals.
You might not like it, but my thought is that Scripture thoroughly demonstrates that Jesus nicknamed Simon "Stone" because of his hard-headedness.
He was a lot like me--usually intransigent.