Plot didn't restrict Sasuke to become JJ.

[Mike D Roberts]

My point is that Sasuke might not have a strong body.

The only Uchiha that had become JJ were using Hashiroids.

Naruto and other Jinchuriki do.

Naruto and Sasuke fought with Taijutsu for better than a half of a day.

Naruto not only is someone with a strong body, but the transmigration of Ashura, who was said to have the Sage's body.

Sasuke could keep up with him.

This proved enough.

 

[Kurama999]

Bijuu cannot die. They are just Juubi chakra.
It was Hagoromo using "Creation of All Things" that created 9 bijuu, as container.
Kurama had to concentrate in order to collect the natural energy and turned it to bijuu chakra.
Just like Naruto, he had to concentrate to collect natural energy to go into SM.