Based on your use-case, it may already been solved. Microservices, for example, are put in a container, which allow you to give read-only\full access to selecte

Based on your use-case, it may already been solved. Microservices, for example, are put in a container, which allow you to give read-only\full access to selected files. They also usually have some kind of Mesh side container that limits connectivity between whitelisted containers or public DNS. And since containers can limit memory and throttle CPU, you are more or less at the best you can get using untrusted 3rd party code.