Numerous people have said Blockland II.
It's not outside the realm of possibility; Blockland's engine is dated and the add-on framework is kind of messy. Honestly, I could see it being a thing. A modern engine (Unity or hell even Source, which is old but it's been updated and still works wonderfully) with a real scripting language (Lua, Python, ECMA/JS, Ruby) and a decent model format (OBJ or DAE, for forget's sake) would be awesome.