It’s a classic stereotype, so why not milk it for all it’s worth?
I wonder if the writers bothered to put stereotypes to all eight sisters? Considering the range of female stereotypes, it shouldn’t be too hard:
1 – youngest – serious and ethical
2 – eldest – serious and warlike, somewhat homicidal in a PG-13 way
3 – bottle fairy
So if we wanted five more ready-made stereotypes, we could pick:
A – Oversexed insecure “nymphomaniac” girly-girl;
B – Bookish intellectual;
C – Nurturing maternal girl who wants to feed everyone;
D – “wild” animal-lover who growls instead of speaking;
E – sweet-and-innocent “imouto” girly-girl.
And that’s just off the top of my head. Because of the gimmick, I’m assuming none of them would be visible cyborgs.