I’d recommend ditching rulers altogether and using layout grids instead. Yes, your suggestions would make rulers much better, but rulers are used in Figma much less often than layout grids. Rulers are good for temporary measurements only. Layout grids are what you probably need to be using most of the time. They are easier to maintain, you can save them as styles, make them stretch with the frame, nest them in multiple frames and much more. This versatility is not available with rulers.