To start with, the shared libraries (DLLs SOs, whatever) should be something MS makes easy for their authors to get inside of an official package distribution c

To start with, the shared libraries (DLLs SOs, whatever) should be something MS makes easy for their authors to get inside of an official package distribution channel. For Windows that happens to be the 'Microsoft Store' and they should be free (as in beer). That would then let MS worry about only the business logic and other glue using that already trustworthy or at least trust-rated code. That too, if it's free of charge software, should have ways of being published that make it easier to verify something is safe, and if it's questionable, then engage in more of a process.