It seems there's no way to change a VM subnet through the App Controller interface. This alongside the fact we're unable to add disks in the private cloud (http://blogs.technet.com/b/kevinremde/archive/2013/01/13/31-days-of-servers-in-the-cloud-creating-azure-virtual-machines-with-app-controller-part-13-of-31.aspx) are issues that are hampering our ability to use App Controller alone and need to use VMM for these quite basic tasks.

Please add this in R2.