Many materials have been use as diamond simulants, including strontium titanate. Wikipedia has an interesting list at Diamond_simulant
I don’t understand your concern about CZ. It cuts very easily. A cutting lap is a combination of metal and diamond. The metals used are softer than most all gem materials, and diamond is a thousand or so times harder than CZ. What’s going to wear out? Even corundum is much harder than CZ.
Of course, I wouldn’t worry about it anyway – for cutting, I usually use 325 or 600 grit on BATT laps, which aren’t going to wear out in my lifetime 🙂
I like CZ. The only reason it’s not considered a wonderful material for gems is that it’s too cheap.