Turns out Bostock explicitly avoided devising Yet Another Grammar of Graphics in favor of selection and transformation operators. Which, as it happens, is a very sparse but expressive grammar anyways (cf dplyr and other corners of the Hadleyverse). Nonetheless, I misrepresented his idea of maximizing expressivity by minimizing grammatical constraints.

The IEEE paper is even better than I remembered. It's just as good today as it was when he first submitted it.