I understood all that, what I didn't get was why she HAS to be played by an Asian, because makeup can make it work once the imaginary casting team chose someone based on talent.
You're not seriously suggesting making up a Caucasian to look Asian?! Reverting to the days of Charlie Chan? That practice was not only racist, it was ineffective. You can't convincingly make a white person look Asian by sticking latex folds over their eyelids. Maybe American audiences in the '40s or '60s, who didn't know or care what real Asians looked like, could buy such a substitution, but nobody with any sense today would fall for it, and no casting director with any decency would attempt it.