I get it; you want a quick way to build the CSS visually. I would say, though, that if you’re exporting CSS straight out of Sketch to be implemented in a project you’re going to be implementing bloated, non-DRY code.
How about treating visuals as a guide to your design – since that’s what they are – and using any additional resource available (CSS exporting, Zeplin, Invision Inspect) as tools to support that guide, ready for writing your Sass (who write vanilla CSS these days?!) in a logical, DRY, production-ready way.
I for one would rather the Sketch team focussed on making a stable, safe-to-use product – in a working environment, upgrading Sketch is a no-go for at least 4–6 weeks after a launch – than adding a feature which can be implemented in other ways since it is only creating a visual treatment anyway.