If you're really concerned about this, just register part of the finger that isn't the tip, and get in the habit of smudging the home button afterwards. I usually only touch the phone with my finger tips or palm, and you could register, for example, a part of the finger under the knuckle that almost never touches the device except to authenticate the print.

Of course if CCC knows which finger was registered, AND has a perfect print left on the device AND they know which print corresponds to the finger registered on the device, of course they can crack it. But if they have to guess which print on the device cracks it, I'm willing to bet they trigger the 5 failed attempts which then requires a passcode (and 10 failed attempts wiping the phone, although this is optional).

This means there are more than 10 options (which finger AND what part of each finger) you could use as a print. The oft cited scenario of police being able to compel you to input your print assumes they know what part of your hand unlocks the phone. They can't make me divulge the part of my hand thats registered just like they can't make me divulge my password.