I bought one of these a while back with the intention to motorize, but instead ride it to the post office as a regular bicycle. When I read your account of the crash this stood out, from owning a Thruster Fixie myself:
I think someone loosened my goosneck overnight.
Mine loosened itself up, even after I went over the whole bike thoroughly when I initially built it. I think the hardware all over the bike, including the headstem allen bolt are JUNK! If you guys motorize these, please replace all of the hardware, because the bolts are soft, which I believe is the cause of mine loosening up. After nut and bolting it a couple times it has stayed, but I don't think I'll motorize mine because I feel awkward up high on the skinny tires because it lacks agility. I bet it feels more stable at high speed with the gyro effect of the 700c's though.
Maybe someday if I get a touring fork and some brakes too, great bike for covering lots of road...