Hi Chintan,
Complementing Amit's info, if you have invested time implementing business rules on BEx queries, the best option might be BICS. As stated above universes can only be created directly on top of providers and there are some anaylisis limitations. Nevertheless there are scenarios where universes might be more suitable.
Please refer to the following link. It covers not only Webi but integration with all the BI suite's tools.
Implementation steps for exploiting your BEx queries with BICS are:
1) Enable OLE DB For OLAP access on your BEx queries (Designer > Open your query > Query Properties > Extended tab > check on "OLE DB For OLAP").
2) Create OLAP connection in CMC (need BW system connection parameters). Specify the BEx query (or infoprovider).
3) On, for example, Rich Client, open BEx data source, sign to BI platform and find the OLAP Connection.
4) Proceed as usual specifying your query on query panel.
Regards,
Fernando