Looking very much forward to see this product in action! Great initiative.
I do think there is an argument to be made that React-Sketchapp, or something similar to React-Sketchapp is a reasonable path to go down with a concept of a branding guideline as a living system of record rather than static, print based styleguide.
The logic here being that the rules that you defined in code using something like React-Sketchapp can be translated and exported out to any environment where the style guide would be relevant. The obvious exports would be to web and mobile apps, yes, but we can export out to Sketch symbols, and libraries that are shared throughout an organization.
I don't know of any non-sketch implementations of the concept, but it seems entirely possible to expand such styling concepts to other programs since, as data, the styling information can be abstracted in such a way to make it compatible with a wider variety of programs.
I agree with this and the fact that we’ve seen so many design systems and library integrations pop up this year is probably proof that you’re not alone in thinking this is a good direction. It would solve a lot of problems.
The only thing I personally find problematic with this approach is that while a brand guideline should be used by the whole organization (sales, marketing, PR, etc.), the design library (normally) only accommodates designers. So integrating works well for when something 'designed' is being produced, but don’t provide any support for other people (who i.e might need to send a logo to a reporter, or check that the color on a slide is the right one, or order new material etc).