My first thought was put the new cells in aircraft, then cheap cars finally grid storage

That's only a valid concept in some embedded engineering case, where a certain capacity is required, and double that amount is provisioned to account for degradation.

Few consumers think this way. Something doesn't have double the capacity that it has; the capacity is the capacity, and the decline looks bad.

But does it keep dropping? Is it 60% at 200 cycles

Going down 10 times faster seems like a really bad trade off for 2 times the capacity. That means your battery will only lst 1/5 or 20% as long.