The unsubscribe page is pulled from our services and has a general view. Unfortunately, this page is not customizable. You can set up your own unsubscribe page and redirect unsubscribed users to it, there is no need to change the basic unsubscribe mechanism itself. More information on this can be found here:
We have already registered the idea for our R&D team to implement the functionality of editing the unsubscribe page in further releases. I will assign your post to this project in order to increase its priority.