Leave Management - have the ability for leave approver to add comments to a leave application

I would like the ability for leave approvers to add comments to a leave application without approving or declining the leave. The leave applicant would then get notified of the comment and it stays with the history of that application. This would be useful as due to resources, we may not be able to approve the leave now for a leave application submitted for 6 months time (so should decline it), but may be able to approve it closer to the date and therefore would like to advise leave applicant of that, so they can then determine if they want the leave app to stay or if they would prefer to move it to another time