I'm pretty sure characters have been built on the assumption that people get sent on from the Mortal World, and appear in Soul Society in a similar body to their mortal one.

In canon, I point you towards Rukia and her sister. They were on the mortal world, then died while Rukia was an infant. Then Rukia grew up in Soul Society.

I don't see why we need to change that, it's a fairly sensible system.