Walt left nothing behind. Right now I'm having computer issues so I cannot post the link to Walt's Florida press conference when he announced formally that he was building Disney World. He, in fact, specifically said that it would be just like Disneyland with a few new things. His focus was so far away from Disneyland or MK at that point that I doubt he would have cared if they just picked all of Disneyland up with a helicopter and plopped it down in Florida. The idea that the parks have to be different is created in the mind of fanbois not Walt or anyone else in the position of making that decision.
His focus was on EPCOT. MK was just a place for people to work and tourist to see as they inspected his community of tomorrow. You don't need 27 thousand acres of land to build a theme park. A national park perhaps, but, not that.