The really bad, quick and dirty cell phone photo above depicts the current state of affairs at the kWsaki EV conversion industries. A very kind forum member from the VMPK forums sent me a 350 mm disc of about 17 mm thick aluminium that I was (barely) able to drill a few holes into. Only destroyed an electric drill in the process of making that big hole in the middle, but hopefully I can make this work. Next I'll have to figure out the coupling between the motor and the flywheel. I intend to keep the clutch as a safety feature, if nothing else. Don't worry, I'll make it look all pretty and black eventually.
Update: A coupler pictured here is now on order!