Good point. The advantage that I am looking to get from unikernels, one that no one seems to mention, is that the whole area of functionality that's above hypervisor but below posix/win32 is suddenly open to play with for application developers.
Think Burroughs, Lisp Machines, Mesa/Cedar, Lillith, Spin OS, Oberon,...
Basically the language runtime is the OS and access to lower layers is done via the type system.
~ Daniel Ingalls, co-creator of Smalltalk http://web.archive.org/web/20070213165045/users.ipa.net/%7Ed...
C and C++ are the outliers here.
Although C++ is moving into a richer runtime, thus increasing the likelihood to write OS independent code without relying on third party libraries.
Even C, if POSIX had been part of ANSI C, would fall into this scenario.
In a way, UNIX can be seen as C's original runtime.