Interesting ideas, but I've got some questions:
Let's suppose that the three great pyramids of Giza, and perhaps some other pyramids from Old Kingdom, were already built many centuries before the accepted dates.
Then: In the case they were built before the global flood (about 10000 BC), don't you think that we should find clear physical evidence of the level reached by the water? And, if some pharaohs were indeed restorers, don't you think that we should find traces of two different techniques, procedures or materials in these monuments?
In my opinion, if anyone wants to break the archeological-historical context of the pyramids and propose a new scenario, must have very good evidence to support that kind of claims.