There really is no reason not to remove the OP_RETURN limit. The pandoras box of indistinguishably can never be closed, and the attitude of destruction will never preclude grinding, even at great economic loss. it becomes one of harm minimization. Your adversary will always have a finite resources, we have to play a longer game.

The strategy that increases protocol longevity (by minimizing active resource cost like [cpu+mem]) is the optimum strategy.