Hi Senthilkumar,
This is too big a subject for an SCN posting. Consider getting a consultant to help.
(Yes, I am available).
Here are some points to consider
1) Without BW and Bex, you lose
a) Language text conversion
b) Currency conversion
c) Unit of Measure conversion
2) Every NetWeaver system, including ECC, contains a BW module. If you really want to make MS-SQL Sever your EDW (Enterprise Data Warehouse), consider leveraging the BW myself system in ECC to install required BI Content extractors and use process chains to post output to Open Hub destinations within the ECC system. I would keep the objects as few and as simple as necessary to get the raw data into your MS-SQL Sever EDW, and perform the transformations in the EDW.
Please don't forget to record your final solution and to mark the question as answered.
Good luck,
John Hawk