80% capacity retention is promising buuuuut.. "near-real-world conditions" is doing heavy lifting in that sentence.
How much does it reduce material and manufacturing costs? I don't expect an exact number, but more like 5%? 50%?
Maybe car companies don't want to do this because they'd rather price discriminate and get every last penny. It would be too bad though, since some people would happily upgrade cars more frequently if they weren't so outrageously expensive ($50k avg price for new vehicle transactions, IIRC).
But it would somewhat complicate manufacturing and make it a little more confusing for consumers to know what they're getting. Perhaps this corner of the market will continue to be served by sellers of years-old EVs, which can have lousy range but work well otherwise.
Modern LFP LiIon (LiFePO4) batteries are pretty damn safe now, and is also the dominant chemistry in new EV batteries and energy storage systems. The fire risk is nothing like what it was, arguably your wish has already been granted.
The Chinese market is mandating this year that EV batteries prevent fire or explosion for a minimum of 2hrs after a cell enters thermal runaway, and LFP is the main driver to achieve it.
There’s a substantial increased risk only with ICE cars that are at least 10 years old and poorly maintained. Li-ion EVs carry that risk from day one.
EVs and ICE cars can both catch on fire in a bad enough accident, but this is true regardless of the age of the vehicle, and tends to be more sudden and violent with gasoline explosions vs battery fires.