One of the challenges with previous versions of the UDI wizard was extensibility. With MDT 2010 Update 1, there was no way to add a new page. With MDT 2012, you could do this by writing C++ and C# code, which at least made it doable, but beyond the capabilities of most organizations. Now with MDT 2012 Update 1, you can build your own pages without writing any code, directly from the UDI Designer.
Here are the basics for doing that:
That’s all there is to it.