Windows 7 has already solution for changing your default printer when you switch network but taking this concept one step ahead, Automatic Printer Switcher lets you set default printer for each application. For example if you want to print images as pdf using tools like NitroPDF or when you print from Word Document you want to use your Office Network printer, this app is good at it.
One you install the application, select the program for the list ( it only displays the running program ) and then map it to any of the installed printer. You can always remove or change the default printer as you want. You might argue that it shows only the running program but its good as there is less of clutter.