Feel sick? Possibly. People are more or less sensitive to imperceptable flicker.

Artifacts?

I bet that can be remedied by interpolating a new frame between every mask frame. Plus, when you mix it down to 24fps you can introduce as much motion blur and shutter angle "emulation" as you want.

Motion blur can also be very forgiving. You are more likely to notice artifacts in still or slow moving scenes and then the problem goes away.