Hi, I spoke to a guy in Germany who modded his Enertia with a beltdrive. Some technical details: Sprockets from Zero-bike, needs to be adjusted for fitting on motorshaft and rearwheel. Rearfork, one tube needs to be cut for placing the belt, after mounting tube is replaced with clamping bushes, he added a springloaded roll for belt tension. Unfortunately i lost the contact-info of the builder.
This is all i can tell you, good luck with modding, keep us informed.