Two of those wishlists css features already exist as specs:
> n-th child variable
See sibiling-index() and sibling-count() https://developer.mozilla.org/en-US/docs/Web/CSS/sibling-ind...
> Reusable blocks
See @function and @mixin draft spec, https://drafts.csswg.org/css-mixins-1/ and https://css-tricks.com/functions-in-css/
Both are available in chrome already.