Commenting on my initial foray into syntax, Mart said:

I think a really important aspect is what the system defaults to if you don’t give it a specific piece of info - like if you didn’t specify sizes for #gc2, it would default to the simplest sensible configuration rather than making cells disappear off the edge of the screen

Choosing what defaults to use when will be really tricky, given how optimised CSS is, but it is really important will have to be addressed before it is possible to write pages at all.