I dont know if you have decided on the tigers ability and its likely that it wont be shown in jjk so here is few suggestions: 1. Teleport to shadows a very big radius and would work as a teleportation and quick travel. You can make it high chakra cost so its not always worth it. 2. Store certain amount of chakra which can then be gifted to the user. 3. Increasingly sharper nails. After each hit they get sharper and sharper. Same with teeth. Hopefully you can get some inspiration from this but you have been cooking recently so I have a lot of trust that it will be good.
Well, having seen everything so far, there are a couple of considerations that I want to tell you. First of all, this is a great idea of what a creative fanfiction crossover should be and without exaggerating anything, even more so when it is accompanied with such creativity to develop the plot I applaud you for that this is currently the best Naruto fanfiction crossover on air that I have read, I just hope it stays on air, it is very difficult to keep up with the pace, I know that, I see that you are including even things that are not canon in Naruto, I just hope that does not overwhelm you, so far the transmigration novel of Kakashi was able to support the pace by including non-canon elements, but as you can see there were several chapters. The considerations that I would like to see are solving mysteries that the series or Kishimoto did not show, such as Hidan's god and things like that, it would be great if you invented something along the way, elements like the weapons of the sage, etc. I also see a lot that you are waiting for some things that Gege resolves, such as the complete domain expansion of the 10, shadows or the shadow of the tiger, which is the one that is missing, although I think you should take the risk anyway, it could give you an idea of the tiger's shadow abilities, such as it could revive the fallen Shikigami with certain conditions, the 10 shadows would become similar to the 6 paths of pain, which is great because Pain is one of the characters that I liked as a use a Kekkei Genkai as versatile as the rinnegan. and some ideas on how you could tame Mahoraga, think of the elephant that accumulates damage by falling or the ox that accumulates damage by traveling, why not make a giant rodent wheel or a highway for the ox to accumulate damage and deal one shot Mahoraga before he adapts like the elephant, I don't know why Megumi never thought of this, but it seems that you have the limitation that for every minute that passes the shadows deplete your chakra, those are inconveniences that you could solve, I just wanted to give you that idea.