Being able to walk slowly without crouching + a use for the ALT key

I think the walking speed is just a tiny bit fast, and while in creative mode and flying, you can't go any slower without descending to the ground. I think you should be able to hold ALT with movement keys to be able to walk slower than usual without crouching. I think crouching/running should have higher priority than pressing alt, i.e. when you press ALT CTRL W or ALT SHIFT W it would only register the running/crouching.