It’s hard to know what will work perfectly for you until you try it but I’d say your design looks like a good starting point and should give you plenty of adjustability if you need to tweak it a bit. The key is to make sure the lower two layers are firm enough to give you the support you need, then after that you can tweak the design as needed (including zoning if necessary). You can move layers up or down in the design as well to slightly change the feel/support (keeping in mind it will affect both). Lower back pain from a mattress is usually from poor alignment so having good support while still allowing travel in the lower back area will be important for your design (again this is why I suggested talalay for the support layers as well).