Well, the Hasegawa model custom has no swappable parts (I believe, correct me if I'm wrong). So perfect transformation should be no problem. I now Yamato is looking for anime accuracy.
But it doesn't need to be 100% accurate.
Detachable legs, or some small parts it's okay to me, as long as it looks good and works fine (although I don´t want a jigsaw puzzle like you said Shin).