We already have option "fast allocation" for primary download path (like a "sparse", but I'm not sure if both works clearly as we want). But if use "move on complete", files moving on destinition partition with incremental copying, what encrease fragmentation by interleaving blocks on simultanious write on drive, i.e. other process writes on the same partition (file system allocate blocks only assume the file size based on the data in the dirty buffer).