You might find Flatpak interesting if you're not already familiar with it. Properly packaged applications start with limited file system access—for example, when you browse file:/// in Firefox, it can't see all your files. However, using the "Open File" menu acts as a file system portal, granting access to selected files on demand. While this isn't exactly how macOS handles permissions, it does prevent the unrestricted system access you're concerned about.