[Rowern]

The issue here is that if you're running in the JS ecosystem you'll definitely want to use other people code (npm package or internal lib), if the subset breaks JS compatibility then you can break a significant amount of code without realising, if it is "only" a TS subset, then you need to make sure that each lib/package you import are compatible. Anyway this does not seem like a good solution.

[shados]

to be fair, even within the TypeScript world that can be a problem. If typescript versions don't line up, or if your various strict options are too strict, you can get into really weird situations. It -generally- works, but when it doesn't, it's hell.