I think what you need is an expandable liner. From what I've seen, if a pool has differing depths, this is what you get. Just check with any pool supply store and I think this is what they will recommend. The liner is designed to expand to cover the deep end. Also make sure you have researched burying an above ground. I read on another pool supply site (I've been doing tons of research looking for a replacement liner, lol) that if you bury an above ground, it may accelerate your rust/corrosion on the walls and actually make them unstable.
I hope this is not too late to be of help. Good luck!