Ability to send Customized message for Request Completion

I would like to send Email notification with customized message to the requestors in following scenarios.

1. When request is marked as complete

2. When request is completed after planned completion date.

I want to send this notification for specific requests not all requests. This is not available in Workfront currently and we have a use case where we need this feature. So it will be IMMENSELY helpful to have feature available.