1. The wear on the driveline will be 10x bigger than normal due to only 4 sliding members.
2. Due to the 4 sliding members, there will be a large torque variation 4 times for each revolution which will be annoying to the user. Remember, gearing is not determined by the radial distance of the 4 teeth sets, but by the radial, instant distance of the chain in the vertical top position. This position bounces up and down 4 times for each revolution.
However, I do find the automatic changing system interesting.