Thank you both for your answers!
Currently I´m thinking of defining a settlement parameter named just as the rate category and then do the settlement for each of those rate-category-related settlement parameters.
This way It would easily possible to adapt the implementation to changing requirements.
Another requirement is to read some product-specific parameter from the installation operands (table ETTIFN). I think this would be pretty much the same since there is a key field "ANLAGE" in that table, too.
As for the BAdi, mentioned by Erik, I still don´t know how this works - since I still have no experience with this technology. If I understand you right, the idea would be to create a settlement unit for each rate category and then select the relevant profiles, right?
If so, I might not be able to use this approach, because I need to do an aggreagation based on company specific criteria.
Well, I will go thinking about the best solution and try a bit....
Thanks again for your help!
Thorsten