Hi Radhesh ,
Check this scenario..
In HR , all employees(having PERNR) may not have 105 IT assignment(means no user assignment). These users can not access fiori leave request service. Because, even if we create a gateway user, to establish the trusted RFC with current user, back end user is necessary.
we had such a scenario for one customer,. They want to make some users to enable leave request without back end user. They were willing to create as many as users in Gateway . We redifined all the odata, assigning a different alais with hard coded users in ECC. The hard coded user in ECC will intern do the leave application service. This is a clear violation of the architecture by the way . You can correlate with your scenario
Sreehari