Wouldn't sending those coins as a(possibly huge) fee be a better approach? That way, those coins get back to the miners and not sent into oblivion to a valid, but onowned, address.
That wouldn't be destroyed.
There is no actual way of "destroying coins". Even sending to an address with a private key that isn't known, a person can also get a lot (and i mean a real lot) amount of hashpower to bruteforce the key. Although it would be difficult, the coins are still recoverable.