I'll have to take a break on writing this, school is retuning soon, and I have lot of things to do now. I didn't drop it, but it will take a while until I be free to write again.

I agree, i think that is reasonable, if the Kaguya clan have a kekkei genkai related to taijutsu, that means they are more likely to have a Yang affinity chakra, and the Hyuga clan have a doujutsu kekkei genkai, which is related to the yin chakra, if the gathering of the chakra of the Uchiha and Senju clan can result in the evolution of the doujutsu to the Rinnegan, that could happen in the same way with the Kaguya and Hyuga clan the only difference would be that they would awake the tenseigan instead.

That's a possibility

Thanks for your suggestions, i didn't plane that long on the future yet, but I'll keep in mind you suggestion.

If they can use it, it means that other persons from there village could too, and that also means the others village are likely to have it.

Well, if you look for shadow clone at the Naruto Fandom, you will find that Ay, Dariu and Deidara had used the shadows clone jutsu.

They have the shadow clone jutsu was spread through all the Great Villages.