I am very much impressed with some of the suggestions.
I myself am looking after the performance management systems. First of all, you need to select a method to assess the performance of the employees. Depending on the technique, nature of business, and number of employees, you will be able to strategize timeframes to develop the whole system.
If you are using MBOs for performance assessment, then you conduct performance reviews quarterly, semi-annually, or annually. If you are using KPI-based performance management systems, you will need to develop performance measures for every department, line, and subordinates while keeping the holistic goal of the organization in mind. You need to have an authentic support document from which you will receive feedback on performance every month.
You will also need to quantify your measures and design calculation steps to measure them in terms of percentages or numbers.
After the whole development activity, you need to communicate how this system will work and execute it.
Now, every month you will receive those numbers as identified in the indicators from every line manager and HoDs. This will help you assess their performance against the measures you have developed, which will later assist you in identifying their competencies, areas of strength, weaknesses. Keeping this in mind, you can devise a training plan for them and process rewards, recognition, promotion, termination, etc.