[DidYaWipe]

BlackMagic does some pretty innovative stuff. They offered an Arduino add-on board that could communicate with and control their cameras over SDI, including access to the Canon EF mount and its commands.

Somebody did in fact create a control board with a knob to control lens focus through this thing. It can be done. The manufacturers just refuse to do it.

[samplatt]

Focus-stacking is a feature on (iirc) the A9 level cameras, which are 5x the price, so it's hardly surprising that they want to lock it down.