There will be times when a staff is on hospitalization leave or compassionate leave or MC or even long unpaid leave and may not have access to a computer, and therefore unable to attach or forgets to attach the supporting documents. So, it will be good that HR can attach the supporting documents on their behalf or even assist to apply leave on their behalf. You may want to include a 'on/off' button. For Company who wants this feature, they can activate the 'on' button and for Company who do not wish to have it, they can deactivate by clicking the 'off' button.