I see, yes I misunderstood the problem.

If a miner sees a block 1x the network average, it would have just cleared out the most profitable transactions. While waiting for the transaction pool to refill, miners should continue to mine those same transactions, ignoring the solved block. If they find a block that is slightly smaller, then they can reveal it to the network. The network will look at the second block, and because it leaves a larger pool of transactions, they would should all switch to the second block and ignore the first block, since their blocks will be more profitable mining on top of the second smaller block. Actually, after every block there would be a short time period where everyone would profit by trying to orphan the known block by producing one slightly smaller...