Oda as mention like to use story reference to his characers/and zodiac reference. as seen above. it's not that hard to imagine. like i mention since Nami got the cat/represented as the cat, which is the Cat Zodiac.This might give a hint to Nami past, since in the Zodiac story, the Cat was tricked by the rat, i seen other version where the rat pushed the cat into the river. so again story reference/animal represented/zodiac traits story etc. So who ever gets the Rat Zodiac/represented in the animal as the rat. will be a link to Nami past. I don't think Oda will skip this detail. because so Far he has not drawn any rats. and only Mice, and sure when he gets to Nami story, we will see the one responsible for separating her from her family, the person will be the rat. this tie to the zodiac story, plus oda represented her as the cat.