Gifting the prime controller back to the foundation or gaw would not be ideal in my eyes as it will be unknown whats happening with it.
Given that a prime controller is really just a private key that lets you stake higher, how can you gift it to anyone? You can give them a copy of it, but how do you un-learn the private key?
And rather than all this scraping, burning, etc. why not just remove the private key from your wallet's config file. Then you won't be staking with an unfair advantage and won't have to worry about how to dispose of the ill-gotten gains.
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.
And your right we cant just give it back. We know the key and without a update it cannot be removed