This doesn’t solve the problem either, which is that of the Confused Deputy [1]. An arbitrary piece of code I’m downloading shouldn’t be able to run as Ryan by default with access to everything Ryan has.
We need to revitalize research into capabilities-based security on consumer OSs, which AFAIK is the only thing that solves this problem. (Web browsers - literally user “agents” - solve this problem with capabilities too: webapps get explicit access to resources, no ambient authority to files, etc.)
Solving this problem will only become more pressing as we have more agents acting on our behalf.
I’ve never seen code that is downloaded run itself. Why not be the change you want to see in the world and run sudo or spawn your browser in a jail. Or download as another user.