If Veloteq's battery system isn't proprietary, you could probably do well by setting your own pack up, but I don't know about what they might have rigged up. I just looked at the Cavalier, as it was the first one on the page, but its packing 48v@20ah of SLA. That would be pretty easy to recreate, and that much battery in lithium for instance, would provide 30% more range, work in all typical temperature conditions, last several times longer in service life, and weigh about 14lbs, as opposed to 62. Downside?

Well, extreme price. I would think you would be facing quite a large price tag.