I like the ice skates idea, Click Maybe it would be leather boots plus some iron ingots?
Also, I think there should be more natural structures. Maybe something as simple as walls around a village, maybe even bridges over lakes near villages. Either way, villagers should gain the ability to build.
Like many other players, I think that the ocean is boring and safe. I'm surprised there aren't any sharks yet. Maybe they can implement small underwater villages that are sort of destroyed. Sort of like Atlantis.
Oh, and I doubt this would ever happen, but maybe erosion and waves. The harder the waves hit the block, the more the block gets destroyed. Each block would have a different durability, which means it would need either more waves or a harder wave to hit it in order to break. Weak blocks would be sand and dirt. Stone, wood, and cobblestone would be harder. But if there were ores it would be the same as stone but maybe drop one of its ingots or ores. If by some crazy chance they made erosions, this could lead to the creation of valleys, canyons, ravines, and rivers over time.
