Wonder if something like this could be adapted to the Z axis to keep it from dropping when power is removed?
Yes. It would have to be belt drive though. Gears have a huge amount of backlash no matter what that increases with every use, belts are much much lower, but belt and pulleys are expensive.
We could always do a servo powered brake? That sounds more fun.
Or, you could drive the z axis up, up, up, until 3" or so, then a trangular latch would pop out, and the carriage would rest on that. You’d just have to remember to pull it back in when you started. If it was mounted well, it would also keep the left and right sides at the right height when you start.
Also, having it sink hasn’t really bothered me, since I leave the motors on all the time. I usually remember to pull up the router before unplugging it.