[MichaelBick]

I personally prefer sanding down hex(knowing that later it will be an easy switch) over trying to make key fit. Even so, if you bey hex stock, bearings, gears, etc. all from one place they generally all fit together well.

I can see how a bushing would be easier to use for some teams. We are able to make spacers and shafts with retaining ring grooves so we don't run into those problems. I like your spacer stock idea though. I think that would be easier for vex and better for everybody else than quick disconnect bushings.