I'm not so sure it's ridiculous. What is ridiculous is that users have no way of restricting what packages can run on a fine-grained level, at both build time

I'm not so sure it's ridiculous. What is ridiculous is that users have no way of restricting what packages can run on a fine-grained level, at both build time and runtime. We should fix that problem. If we do, then we could make computing a lot safer. Disclaimer: I'm working on that problem.