[@Buddha]Well, I was wondering something about the fact that he's constantly venting Nature Chakra while wearing the seal. Could most people sense that, or just thus in-touch with senjutsu? It's been awhile since I last watch Naruto and I forget the specifics of the natural energy. In my mind, it just melds back into the terrain that surrounds him easily and mostly discreetly, but that could be changed to give Shizuka another weakness.

Another drawback could be intiated if the rules atround the Kekkei Genkai could be bent a little, namely him healing others using Cellular Regeneration Ejection. In the anime, Jugo could only seem to do this with Sasuke because of the curse seal, bjut I want to broaden that to others to further Shizuka's support role by enabling him to help either heal or at least stabalize people usung the technique. Of course, doing so means that, like Jugo, his physical state and appearance revert to that of his younger self until he's able to replace it, which he can only do as Yūrei.

Other than these two things, I'm kinda tapped out for what else can be done to weaken him.