Let me appreciate your efforts in drafting the policy. As a trainee, you have done the job far than better.
Any policy should cover as much details as possible. For instance, the age eligibility can be written as, "Employees who attains the age of 58 per the date of birth recorded in HR system". At least in India, we can see duplicate date of births as the original date of birth would be something and the certificate shows the other, clarify this.
Aims can be written as "Objectives"
Any idea of early retirement? For example, an employee reaches 56 years and wants to retire, do you have any process for this?
Is it possible for you to make quick FAQs on this policy, while you try to draft FAQs you tend to ask more questions from employees point of view and thus the policy will cover vast details. Policies with FAQs will reach better to employees.
Benefits - Hope you will list the benefits that will not cease, if not please mention that, benefit entitlement details will be notified along with your retirement package email.
I appreciate the process workflow (Notification > Application > Assessment > Contractual Reappointment)
Some more details on how the compensation and benefits will be treated if employee continues to work post retirement age. Employees may ask questions related to this.