Bizarrely, I want to make a Minecraft mod.
And it's just not the same.
The only solution implemented by the developer is permadeath, where upon your character's death the world is deleted. Which is ok, I guess, except that the game still gets too easy once you get your foothold on the world. Your walls are up, your homes are safe, and there's nothing left to do with yourself but continue to build elaborate palaces and hope that you don't make the single stupid mistake that results in your death.
No, what I'm looking for is a world that gets continually harder, one that strikes out against you no matter what you're doing. I want the zombies to be aggressive, feral, and deadly. I want them to slowly and noisily tear down your walls while the wailing attracts the other zombies. I want the skeletons to appear in groups and fire flaming arrows that turns your abode into a flaming ruin. I want spiders that can climb anything and poison you such that a single bite means your death.
And when all of that happens, I want you to spawn away from your house. I want for there to be nowhere for you to go back to when all is said and done. I want for you to have to pull yourself up by your bootstraps again, and always be on the alert for yet another attack. I want it to feel like you've accomplished something when you've survived for six nights, not like you're doing struggling and it's time to farm the grains again, or to see how the pigs are doing.
I think an experience like that would be a lot of fun in a sandboxed Minecraft world. After all, what's the point of giving you a world to explore when the world itself isn't even very interesting?