Seems there's wiggle
>room too to explain that the curse seal can be a hacked up
>sage mode or some crap.
>

It's what its always been.

The seal is based off of Juugo's clan ability to absorb natural energy (what sage mode does). Juugo's clan doesn't have to learn how to absorb natural energy, but they also can't use it effectively like Naruto or J-man. The most they can do is transform into creatures and augment body parts. Even then they go mad when they use it.

Oro's knowledge with Juugo's and Oro's DNA is the cursed seal. Oro has tons of hideouts and dead prisoners as research.

Juugo also has the ability to give out chakra. Only reason Sasuke ain't dead now is because Juugo gave Sasuke chakra after Killer Bee blew his fucking chest open.

Sasuke pretty much mastered how to use the cursed seal before it was taken away.

And now here we are. Juugo lent Sasuke chakra so he could utilize the natural energy.