How does access control work? There are plenty of APIs that need to validate access (e.g. ping or raw IP sockets can require sudo). If it's all running in-process it seems like there's no security you can implement, or the security mechanism would end up being super-complex like inspecting the TCP packets (which may solve networking use-cases but doesn't do so well for all the APIs).

*EDIT: Unikernels are neat as replacements for VMs since the abstraction layer can be much less costly/higher performance. They cannot be used as regular applications running on the OS due to how security is implemented.