Thanks for the upgrade!

Thank you for the thoughts, however, I'm not buying some oddball used pool from the 80's, it's going to be relatively new. I called a pool store and they said any buckling of the wall compromises its integrity. I'll give the first few I saw (with minor buckles) a skip. Looking at another tonight that's 4yrs old, Aqua Leader. If the walls are in good shape and the rest of the bits accounted for, it will be coming home with me. Will just need a new liner.

I'll skip the dished bottom. Would have been fun but not fussed either way.

Can I line the bottom with foam or do I have to use sand?

If I wanted to slightly build up a low spot (slightly = about 6", maybe 8" tops), what material can I use (sand / rock flour, soil, gravel with sand or soil on top, other)? I presume I'd need to rent a compactor to get it flattened properly. It would mean a lot less excavating of the rest of the pool footprint (the low spot is maybe 1/5-1/6 of the total footprint of a 24' pool). Not to mention, it would look better. I'd prefer to do this if I can, but I don't necessarily have to.