This is actually something I thought of a few days ago and brought the same issue up here with the other solo pool providers that I know are mintting addresses that you mine to into the new blocks. So they would mint a new block with a dev fee address.
Our pool does not put the mining address in the block so I would have a chance to intercept the block reward. The only problem is the pool is anonymous and as far as I can tell there is no log of a miner switching to another address so I would have no idea who actually got the block.
I will try to think of a fix for this that doesn’t invade privacy. But for now if you mine with a miner that switches for dev fees, you have a small chance of losing the block.