Sorry, but this sounds illogical to me. How introducing some additional new CSS syntax is less Yet Another Syntax than just using some already established (but not popular) syntax? SASS has its user share (and easy to learn too) and new syntax has no users at all.

The new syntax has no users at all sure, but CSS has far more users than SASS or LESS will ever have. You're asking web developers and browser developers to learn and support a completely different technology, rather than adding an incremental, much needed improvement to something that has been used for many years.