Dear Praveen,
As far as i know the ECR/ECO process is based on the SAP Business Workflow.
You are right, there are several apps for specification use cases but not suitable for your use case .
However there is the Approve Request Fiori app:
To my knowledge this can handle all processes based on the Business Workflow.
Might require some customization but in general it should work.
I hope it could help.
Regards,
Gergely