You put an idler in the middle for a 3 gear train, that keeps the proper spinning direction in place.
I envision problems with that SOHC design, the sprung hub is going to be an issue. The DOHC one survives by using much smaller damping mechanism there, and even that may be gone now to use just the clutch basket as the damper there. Can't say. The first one used the OEM shell and the outer disintegrated under hard power, the inside damper blades that were separated by the damper rubbers moved under big power to crack the whole thing up.
You want a crank damper to absorb vibration, it stops crankshaft breakage, but you also want solid gears there to carry bigger power. The SOHC gear shown in the link is likely to break up under power, the spring damper renders it too weak.