"Since the beginning of mankind, the fable-tellers have not only given us entertainment but a kind of wisdom, humor, and understanding that, like all true art, remains imperishable through the ages."
--- Walt Disney
Mythia was originally to have been located in the Discovery Bay section of Disneyland. However, DCA has set the precedent for new parks, rather than crowding Disneyland and dilluting its themes.
So, Land of Legends could easily be a park unto itself. Really, Greek and Roman myth could be a park unto itself, but that does seem a little odd. Instead, I think you could reImagineer World Showcase as an exploration of the oral traditions of places around the world.
The trick, I think, is to incorporate certain stories without automatically making a tie-in to the Disney film. For instance, an English pavilion would naturally address King Arthur, but not through the Sword in the Stone film. Instead, they may want to use existing concepts for AK's dragon ride in the Beastlie Kingdomme proposal, and re-work it to Merlin's prophecy to Vortigern, in which Vortigern's tower rests on the den of two warring dragons. Or, perhaps as Sir Gawain's battle. Similarly, instead of Hercules, a ride could be based on Perseus and the killing of the gorgon.
Skew the park a little older in theme. If there's one thing I remember from childhood, kids want to be treated like adults. As long as you create rides that the whole family can ride together, you can make the content a little darker and kids will eat it up. Plus, the American pavilion can include Paul Bunyan, Pecos Bill, and Johnny Appleseed, this time the Disney versions.