If your requirement is to develope a report on Master data then the best approach in your case is to load the customer master data to a DSO rather than to InfoObject .
The key fields of the DSO should be the InfoObjects which u were trying to compound to Customer Infoobject .
Once ur DSO is ready ,map the generic datasource which u have created to this DSO and load the data.....
This should work fine in ur case .....