How to clone wp-admin and make a new dashboard controlled by your code?

Let's say I want to create a new admin panel for WordPress. Which should be separate from the one we have now. How do you think I should start?

I want to build /wp-admin/ from scratch for administrators. Which means, the new admin panel should have everything /wp-admin/ has. Why need to build a new panel? Because the present one keeps changing, and what I am upto needs an area which is under my control, and not changed by every WP update, but I update it when I want to.

Summary: I want to build root.com/dashboard/ which has everything present at root.com/wp-admin/

How do you propose I begin? What is necessary to make a completely new WordPress admin panel work. Which files, permissions, sessions etc I should be looking at. Looking forward to some pointers from you guys.