Alright, I want to make sure I answer all your questions, so let me know if I leave anything out, haha!
Re: using the same files – our use case is actually pretty similar to the one you describe at the end of your comment. We also have an application for our Component Library that includes the Storybook UI as well as the components themselves. This blog post describes an approach VERY similar to what we do. Currently, all our apps have the component library added in the same way you would add d3, lodash, or any other external library, so keeping them updated is as simple as running yarn upgrade 'component-library'.
yarn upgrade 'component-library'
Re: zooming out – in an ideal world, yes. But in a more practical sense, we already had 3 different applications with similar (but not exactly the same) UIs. Our hope was to start creating components that could unify the visual look, so our suite of applications actually felt like a suite – to try and get an "easy win" on this front, we opted to start replacing small components (like buttons, form inputs, etc) to start creating consistency. In doing this, we felt some chafing re: integration of new components into various existing UIs. I think a "pure" Atomic Design approach probably could have fixed this, but only if you were willing to do ALL the design upfront in the Component Library, and not start to implement any of it in actual applications until you had all of it figured out – we opted to start implementing small pieces and adjust as we went. In the long run, I still feel like this was the right move – it's a little bit more agile and iterative, and that fits how we tend to work as a company.
Hopefully this was helpful!
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