Saket,
There are many deployment options. Even with Central Hub Deployment, there are two options. 1. Development in Gateway 2. Development in Backend(ECC).
In your case, it makes sense to do development in backend. You need IW_BEP wherever you are going to do development. But development on Gateway can be tedious, since you have to create RFCs for all your requirements. Rather I would go for development on backend and install IW_BEP in backend. So your data modeling and service implementation will be in backend (SEGW) and service registration will be in Gateway(Hub) system.
regards
Krishna
