I was vaguely aware that there was something in this space already... I think it used be known as Virtozzo? Anyway, I wonder how well it can work as a layer on top of the Windows OS rather than being integrated as I imagine only MS could do.
There has been an initiative inside of MSFT called project drawbridge which has in place for 4 years to do this. They have given up on it...the problem is isolation and there is not clean way to isolate registry. Azure was an attempt to do this and it ended up being super restrictive for any real world apps.
I'm sure Hyper-V does some sharing of memory pages related to the Windows kernel when running multiple Windows VMs (if they are the same version at least), but there's probably an opportunity for an approach that is lighterweight than VMs but still gives you a greater degree of isolation than just a managed boundary via the CLR.