your wishlist has a name, jQuery
Neither constructive nor accurate.
The proposed cursorX or cursorY value, for example, would immensely simplify implementing a magnifying glass or Pikachu chasing the mouse cursor or whatever.
The :parent selector, while annoying in implementation for browser devs, would help a lot with certain clever effects (easiest being, say, drag-and-drop) when used properly.
round, floor, and clamp speak for themselves.