Hi Duncan,
Your idea sounds very interesting! But could you please provide just a few more hints? In particular, I gather from http://blogs.vmware.com/vipowershell/files/2012/12/image.png that PowerCLI requires vCenter Server itself as it speaks to the same vCenter API as the C# and Web Clients. Or can it speak directly to the ESXi host API, like the C# Client?
Thanks a lot!