We use advertisement with transforms on NT 4.0 to install office 2000 applications. We have situations in which outlook, frontpage and the other office applications are seperately used. I.e. a user has outlook installed(advertised) and en the user gets later frontpage. It is not possible to advertise frontpage because the product (read Outlook with the same productcode) is already advertised and installed. I know that it is possible to advertise mutiple transforms but then you have to know ahead which applications a user gets (this is not a realistic situation for us).
You could create transforms for every product. Make sure you also change the ProductCode, PackageCode and UpgradeCode (this may break future major upgrade). I believe there is some info in 'Instance transforms' in the helpfile.