You can do this with a logon user script through group policies (i.e put it in as a user scripts section rather than computer)
This will then can be used to assign a printers with the ‘net use’ command. If you use the /persistent:no this can be set everytime with the batch script (recommended, you get warnings and can more easily change)
This way you can set different default printers for different groups.
The only problem I ever had with this was setting the default printer on a per machine basis, as you can only add a printer with the user logon.
With some messing around I imagine you could use a list of PCs and an intellegent script to set the appropriate default.