Can the end users pick the operating system layer to use with Unidesk?

With Unidesk, you could easily create two desktops, one provisioned from a Windows XP layer and the other provisioned from a Windows 7 layer, and let the end user choose which operating system to access.  But O/S layers themselves are read-only, and cannot be selected by end users.  O/S layers are created and assigned to desktops by desktop administrators using the Unidesk management console.  Users can install applications and even upgrade Windows themselves if you give them administrative rights.  All of their changes would be contained in their own Personalization layers, however, giving you the power to roll back their changes, or promote the files and Registry keys from an underlying IT-assigned layer at any point to resolve a conflict.