What do you think about upgrading Hinata's Byakugan?
The Uchiha clan's Sharingan can be upgraded and later evolved into the Mangekyo Sharingan. So, why can't the Byakugan be uprgaded as well?
It's a fanfic, after all. You can make it so her clan never realized this was possible because they only ever trained in the Gentle Fist, but Hinata has been training in other disciplines and maybe she stumbles upon something, which leads to a new level of Byakugan?