I read your link but none of those definitions of “keepa” are anything upon which a church could be built. They are however in line with the Hebrew “keph”, which may not be the “hollow rock” that Strong’s describes, but is also not the substantive rock described by the Hebrew “tsur”, the rock foundation for the city of Tyre, and “cela, selah” which incidentally became the rock city we know today as “Petra” — not “Petros” or “Cephas”.
But I'm not sure that matters. The point is that it's the same word at the beginning of the phrase and at the end in Aramaic. Keepa....Keepa.
Let's take this to the insanely ridiculous and say that Keepa means styrofoam:
So "Blessed art thou, Simon-Bar Jona, for thou art Styrofoam, and upon this Styrofoam I will build my Church, and the gates of Hell shall not prevail against it."
As we know from John 1:42 that Keepa/Cephas was Peter's original name, it substantially strengthens the argument that Greek Petros/petra is just a simple accommodation of gender and does not intend to highlight a difference in meaning. There is certainly no evidence from the Syriac Gospels that a different "rock" word was used of Christ in this passage.
So even if Petros means "hollow rock" or pebble or dustbunny, still the Church stands upon it. If that should strike you as illogical and dangerous and almost insane--it should. Because it is.
To apply a C.S.Lewis quote: "He's not a tame lion you know."