One last comment before i get back to work
If we were to stop staking nobody would be able to verify we actually stopped. We could have just moved to a new address with new coins.
It's trivial to examine each block and see which PC key if any was used to stake it. We will already need to do that to see which addresses you're using the PC key to increase your staking rewards with. There's no guarantee that the one address you show that you're gaining increased returns on is the only one you're gaining the unfair advantage on.
And your right we cant just give it back. We know the key and without a update it cannot be removed
Similarly it couldn't just have been given to you. Whoever gave it to you can still use it.