Double thick ceramic is worth using. It doesn't have the same deepening affect that can be awesome with alnico, but it does sound slightly less abrasive than regular thickness. But at the same time it boosts the output and makes it more in your face. So it doesn't really warm it up like double thick alnico. Mostly if you just want max output. Think of the pups it comes in. Black Winter, Invader, Distortion, etc.
You can use ceramic with alnico, but a double thick ceramic would run over any alnico you add. You're best off using alnico in the middle and ceramic spacers for a good balance of both, or even 1 ceramic spacer.