Fuchsia is looking like a neat contender for tackling this problem. I've read through most of their design docs, and if I've understood them correctly, it should allow for fully recursive processes. The sandboxing [0] and namespaces [1] design docs are a good starting point.

As an example of this in action, the test runner [2] creates a new application environment for each test.

[0] https://fuchsia.googlesource.com/docs/+/HEAD/sandboxing.md

[1] https://fuchsia.googlesource.com/docs/+/HEAD/namespaces.md

[2] https://fuchsia.googlesource.com/test_runner/