Pretty nice design! I'm building something similar to this right now. Here's mine: unlike yours the speed difference between both outputs is compared using a differential. When both run at the same speed the output speed of the differential is 0. A rubber band is connected to that output in a way, so that there needs to be a speed difference big enough to stretch the rubber. The locking mechanism is directly connected to the output and thanks to the new orange rotary clutches it doesn't matter in witch direction the output turns.
What do you think about this?
I found it to be the most reliable and compact design i could think of, considering that you can use a pneumatic cylinder instead of a rubber band in order to change the locking-behavior.
Keep building this amazing stuff, your build inspired me a lot!