I've been thinking a bit about another take on "1950s sci-fi" myself, although my thoughts were running a bit more like "after flying saucers, what else did movies feature then... giant monsters!" The problem is that I'm aware that Steven Spielberg was resistant to do "aliens again," and he might be just as resistant to do "dinosaurs again..."

Another unused idea in "The Making of Indiana Jones" was the "Monkey King" legend. I suppose, though, that I usually try not to speculate too much, the better to not wind up judging against those airy speculations...