So many good ideas here! I just bought my HalfBike used from a person here in Dallas, TX US for $25. He said that he and his step-dad tried it three times, both fell, and gave up. Unfortunately, it has a single speed hub that doesn't work well in my moderately hilly neighborhood.
I've reached out to HalfBike about getting a kit to upgrade to a geared hub, but haven't heard back yet. In the meantime, I've been looking at options and stumbled upon this CVT hub that is infinitely adjustable between a .5 underdrive and a 1.65 overdrive. I still have plenty of practicing do to before I pull the trigger on the new hub, rim, tire, and spokes, but think it could be cool. I can also mound a disc brake to it, which could be pretty nice to as the HB2 brake is underwhelming.
Besides the gearing, I definitely want to figure out some lights, pedals, and bar end grips. I guess it is a good thing I got my HB2 for so cheap!