Obtaining a Class 2 medical certificate for a UAV Controller Certificate is optional.
It is not a requirement by CASA to obtain a Class 2 medical certificate in order to obtain the UAV Controller Certificate.
It MAY be a requirement by your UAV Operator’s Certificate holder.
If an operator decides (for various reasons) during the process of writing the Operations Manuals that all Controllers will require a Medical Class 2 certificate then you will need to get this before submitting your controller certificate application if you wish to operate under that UAV OC.
It may also be a benefit in order to getting better UAV Insurance Premiums or required by your clients but it is not required in order to get your controller certificate from CASA.G+