What you are describing is just dangerous, for the simple fact that people then think they are safe, as soon as they put the battery into salt water. You even say yourself that it takes days until fully drained. During those days, the battery could still ignite. When that happens, the salt water will not help at all. What then will happen is, that the water will immediately turn into steam. You know what happens if you put water into hot oil - similar effect, just less dangerous. The water will be gone in no time and everything around it starts to burn.
That‘s why we always recommend what I was suggesting in my initial comment. And please don‘t say things like „it is the only fully safe way“. This is just straight up wrong.