I'm not suggesting that miners engage in a wild scheme that acts against their own self-interests.

I'm pointing out that they merely need click a box and lose orphaning risk from adding new transactions. Miners who do this will be more profitable, even if some did not-- they will be out competed by more profitable miners who do, end up operating at profit levels that are uninteresting and exit the system.

It is _locally_ more profitable for them to do so-- the scheme you describe is NOT an equilibrium. Any miner can add a commitment for what they'd like to include and do so at no cost. Any miner can use any existing commitments to decide to include transactions earlier. No coordination is needed-- beyond the one time act of someone writing the software, no orphaning cost taken to move out of that state.

Miners making local decisions that are somewhat adverse to the health of the network but profitable for themselves is not a hypothetical-- it's an observed effect. Without it we never would have had huge mining pools, to give one example. (arguably: we'd have no GPU or asic miners, either!)

Expecting miners to continue indefinitely to take considerable orphaning costs against their own self-interests in order to uphold some abstract 'good of the network' that comes from the 'virtue' of orphaning is isomorphic to expecting them to just pay a $1 sin tax for every transaction they include without any enforcement mechanism. They simply won't.  

Even if you assume the existence of some conspiracy to punish people who behave locally rationally-- and ignore the potentially devastating effects this would have on the other properties of the system--, these schemes can be arbitrarily undetectable... anyone who didn't like it couldn't even tell it was happening.