I think your version would be 10000 times faster than SC. Honestly - SC has a huge runtime cost, which is not measurable on small Apps, or Components, but would strike you later.
Remember the performance path SC has went - they were terrible slow in v1, even slower in v2, become 10 times faster since then, and double that speed at v4. There is almost no room for improvement, and it still 10-100(!) times slower than "pure CSS".
If you want SC-like CSS-in-JS - linaria should be your friend.
If you value customer experience over DX - go BEM way.
I think your version would be 10000 times faster than SC. Honestly - SC has a huge runtime cost, which is not measurable on small Apps, or Components, but would strike you later.
Remember the performance path SC has went - they were terrible slow in v1, even slower in v2, become 10 times faster since then, and double that speed at v4. There is almost no room for improvement, and it still 10-100(!) times slower than "pure CSS".
If you want SC-like CSS-in-JS - linaria should be your friend.
If you value customer experience over DX - go BEM way.
It depends on use case
necolas.github.io/react-native-web...