KernelSU has something like this called app profiles where you can set the capabilities that each app gets when it uses su. And if you are a SELinux wizard you can also set a custom domain for each app which would give you the fine grained control you’re looking for. I doubt the average KernelSU user wants to delve into SELinux details so some tool to automate this would be cool. Sadly doesn’t look like Magisk supports this.