Since it's all supposedly based on intent, it would be really cool if it would export an annotated set of screens at various sizes. Perhaps looking similar to Sketch Notebook.
Things like (this is super rough):
"The main navigation should always be 16px from the top of the screen and be centered 16px spacing on either side."
"Each switch toggle should have 4px padding and be at least 24px below the previous toggle switch."
"[The {box} || Each {class}] should [ have || {condition} be ] {parameters}"
or something much more clever.
The other thing I see working well would be 'export modes': different export methods that would output completely different formats based on intent, i.e.:
Styleguide export = like the above, but with extra pages outlining typography, color, maybe even each component in detail.
Prototype export = rough html & css that's just good enough to demo or first draft an interaction. Bonus points if we eventually get the ability to do fixed positioning or link between artboards.
Static export = similar to how Sketch handles it, as a 'stack' of screen sizes and image formats to be generated all at once.
Any others you'd want to add?