[rwmj]

Let's define unikernels as running under a hypervisor.

I don't think this is a useful definition. Our unikernel Linux (UKL) can build a unikernel that runs direct on baremetal, and that's a fantastic feature and also quite different from embedded OSes.

unless you're running at massive scale

That's your opinion. We are intending to deliver unikernels to anyone who wants performance and/or real time guarantees. They don't need to be operating at scale.