Apologies if the reply goes to the wrong location in the thread. 

"... At least with Xen/KVM/VMware you're running on your own virtual disk..."

Can't the virtual disk just be mounted by whoever has access? I don't think this is a large barrier to entry for anyone or a script looking for private keys. I could argue that pretty much every mac user has been getting software in the form of disk images, and these possibly non-technical users seem to have no issues.