Island! It would make a surviving 100 days on a desert island (deserted tropical island) possible in vanilla, adding a nice tropical vibe to places like warm oceans with some coral reefs nearby, etc.
or End update
I had a cool idea, every like 8 or so updates, they package up every unused thing from past update suggestions, like adding things like the Iceologer, or the Illusioner, and the Master Blaze, and unused biomes, etc.