Nicely done ! An idea to make the drum/tank drive even more universal (in place of only Jobo magnet coupling) might be to have one driven square shaft with longitudinally adjustable 'wheels' to transfer the rotation and then another, moveable, undriven shaft to provide the other half of the support for the drum/tank. Like many people I had vague ideas about a Jobo replacement, but you have progressed much further !