Hi,
Assuming you have deletion flag for all the records which are getting deleted . You may create generic extractor with View having condition to filter deleted records.
After creation of this generic extractor you would have to change delta type in table ROOSOURCE to "AIED" in the database.
Once these chagnes are done , replicate this data source in BW and extract data . You would see that it will delete data from BW DSO.
Hope that helps.
-Mr Kapadia