To be honest, I actually find that to be a bite of mute point (with the exception of foot samurai set where all the torso where in 2 parts and even that wasn't too hard), no real hard part is always attaching the arms and head which is actually more difficult with the newer sculpts some of which feel like they are supposed to be one pose sculpts (that really need instructions), I actually think that separate torsos and legs would be more freeing.
The Rising Sun kits had a few design flaws, nice as the models are. Nothing that can't be worked around, but the two part legs are probably top of the bill. But I think you can see from more recent releases that they learned from that. WW2 kits were torso+legs and everything after that was one piece bodies.
because I have nothing better to do, I shall cast thread necromancy upon this forum. a few months back I played through Call of Duty advanced warfare, now I know we've gone over the Mask/open face topic to death, but that can be solved with two head options for the sprue, but I think the marines from that game, basically tick all the boxes: