I understand what you are saying, but you need PROOF that the address belongs to you and that proof is the private key.
What you have described is more or less the "normal" way to mine blocks.
No, the proof is the hash that you send the masternodes first.
This is what happens:
The miner sends 6 randomly picked masternodes (that everyone agrees on) an sha2 hash of: their found block + transaction from the private key that everyone must use to mine's address to their own address.
Then the masternodes respond with: Ok, if that sha2 hash turns out to be a valid block + transaction to miner's address, we will add it to the blockchain.
Then the miner provides the block + transaction to their own address.
The masternodes then sha2 hash it and if it matches the first hash provided by the miner, they add it to the blockchain.
Or am I still wrong?