These are very good theories. Yes stepping is just one thing, the switch can be even invisible like 2 “special sqms” on Rook to make spike sword disappear.
What else should we consider… Maybe manipulating torches on the walls? Or spilling liquids on sqms? The possibilites are pretty much endless. Surely we need to carefully analyze the environment – the hints may be hidden so well, that we can’t notice them even after many years (just like with Samael for example).