Hi Niket,
you are right, SAP NetWeaver 7.30 is not supported for SAP NetWeaver Gateway.
http://help.sap.com/saphelp_gateway20sp08/helpdata/en/52/fc994f456a4573957461be15520fe8/content.htm
The BW integration is part of the AddOn IW_BEP and it is remote enabled. As a result you can generate the BW based OData Services on the Hub System if you deploy IW_BEP in addition to GW_CORE and IW_FND.
You can install the Gateway Server components on the ECC system itself (provided it runs at least on top of NetWeaver 7.02) but I would recommend to use (if possible) a standalone Gateway Server (with IW_BEP deployed for the BW integration).
Kindly check my following blog about the different deployment options
SAP NetWeaver Gateway deployment options in a nutshell
Best Regards,
Andre