Hi Baldeep,
Nope. In our way also we were using the same method to extract the data out of the planning books, i.e build a DS in the source system and replicate it to BW. Please make sure to have the below points in mind before extracting..
when are you planning to extract the data i.e daily or weekly?
How much amount of data are you looking at?
What level are you going to plan i.e material level or material location level ?
Is it going to be a weekly snapshot or daily snapshot ?
You have to data model very carefully when you are planning to take a weekly snapshot.