Yes we know the original Kyosho 's CVT is a continuous-variable transmission, and typical CVT using Belts and pully and by changing the diameter of contact path of the pully change gear.
CVT is a good idea but when applies to 1/9 kyosho seems to have reliablilty issue due to the material used. You probably know more than I do in this regards,
Just now I see it's a bit different in your setup then I ask if in your new gear box it's still a CVT...