We had raised an OSS message for this and SAP has responded back saying that the current version of the application doesn't support this functionality and they have already considered this feature and working on it.
However we can achieve this using Extensibility
Links:
http://help.sap.com/fiori_bs2013/helpdata/en/b8/7e4352b4e61b13e10000000a44176d/frameset.htm
App extensibility : Leave Request
http://help.sap.com/fiori_bs2013/helpdata/en/55/20cd5262411642e10000000a44176d/content.htm