Could the workflow for approvals be extended to include the users line manager, as many processes and approvals do not require the department head level of authorisation to proceed.
There is currently an operator $DEPT_HEAD$ which will assign the users department head as the authoriser.
An additional operator for $LINE_MANAGER$ could be added to assign the users line manager as the authoriser. This line manager could be imported from the users active directory account and displayed in the my details section so it can be changed if required.