Hey, Fusemastah,
That's surprisingly similar to how I plan novels. Or maybe not surprisingly.
Take two different mythologies, bounce them off each other, and whammo -- idea that PCs didn't see coming.
My current d20 Modern campaign -- which, arguably, boils down to "Secret Battle against Werewolves and Mermen Using Alien Tech" came from a ridiculous attempt (by me) to handwave a way for both the Land-bridge-from-South-America-to-Africa theory of Atlantis AND the Antarctica-used-to-be-temperate-but-the-crust-shifted theory of Atlantis to be correct (when, according to most scientists, neither theory is correct, by any stretch).
Long long time ago: Race of early humans found alien tech, advanced extremely rapidly. Conquered its small continent, kept other humans as slaves, worked on plans to wipe out rest of humanity in order to wipe slat clean. Alien tech included gene-resequencing and mass teleportation devices. These guys were the Old Atlanteans
Long time ago: Slaves of these guys found out what was gonna happen and rebelled -- they teleported a large section of the continent of Atlantis partway across the world, also activating a doomsday device that would repolarize the Earth and shift Atlantis into the antarctic zone.
Some time ago: Old Atlantean survivors adapted themselves by resequencing DNA for cold-weather adaptation and survival without most of their technological resources (ie, they grew fur and resistant to common weaponry). Unable to mount an assault against the New Atlanteans (the descendents of the slaves, who established their own indomitable island with the best remains of the Atlantean tech), the Old Atlanteans opted for revenge, and used their teleportation device to rip New Atlantis from the middle of the Atlantic ocean and drop it to the bottom of the Pacific (where nobody is looking for it, where no research ever puts it, and where it is soley to make it easy for my PCs to get to it, since the campaign is based in California and Washington state).
A little while ago: The New Atlanteans survived briefly at the bottom of the sea, since they possessed energy shield technology, and were able to resequence their DNA before it failed and let the water crush them and most of their city. They opted for a new form that would enable them to survive underwater (ie, gills and other amphibious features).
Today: The PCs scrounge around for all kinds of Antlantean ruins, trying to figure out why some sources say that Atlantis was Antarctica and some sources say that it was in the Atlantic ocean, but nobody ever says it was in the Pacific, which is where it seems to be now. And werewolves and merpeople keep attacking the party to recover artifacts, and the PCs have no idea why.
Two mythologies get smushed together, and voila -- metatextual campaign, sorta.
