I don't think the karma seals require a physical body to exist. The holograms at the monument are probably all that is necessary. Another thing is that Kaguya's rinnesharingan is not sealed in her Hologram. Somehow they bypassed the seal or it was prepared beforehand.
Boruto is a good vessel because of the Jougan more than likely. They have a whole ten tails in their pocket how does it not have a body?
Its different with the karma seal. Momoshiki isn't being suppressed like Kurama. He is just waiting for Boruto's body to adapt to the karma seal. I would give him some 9tails chakra so Kurama could scope things out.
Kawaki is a prodigy with a scientific body. He's probably as good as it gets other than having some crazy kkg which he may have.
Hologram? I think those are just informative things. Like profiles and such. Probably for Kara members to learn.
It is widely known that Kaguya took the fruit for herself. We don't exactly know what that fruit entails. Since Isshiki is gone, it could possibly be that Kaguya made him into a fruit. It could also be that the stories were true and she turned the God Tree into a chakra fruit and fought Isshiki and that is why he is gone.
It could be that Isshiki sacrificed himself and made fruit. Kaguya absorbing the God Tree to control the world and turn people into White Zetsus. Isshiki turning human and that is who fathered Kaguya's twins.
It is also quite possible that the twins were just made by Kaguya out of nothing.
As for the whole Kurama and Naruto thing, I was merely using their relationship as a parallel to what I think Boruto's relationship with Momoshiki, if it truly is Momoshiki.
Ikemoto is consistent in drawing parallels with what we already know and building on it, which is predictable. But it is preferable this way since it won't be an asspull and it is satisfying to actually have some consistencies.
As for Jougan, it is heavily hinted that it is basically the Mangekyu but for Byakugan. So I doubt that the Jougan is more special than the Rinnegan or Tenseigan.
It certainly is a first as the Hyuga were careful enough to seal their eyes so it can't be stolen.
I'm still not on board with the Jougan though. At the very least, have the Jougan exist in both eyes rather than just one.
He doesn't have to be anti-Sasuke, who tries hard to be Guts from Berserk (yes, that is why he has the left eye and the amputated left arm because Guts lost his right eye and his left arm).
For the ten tails, Momoshiki already stated that beasts are merely chakra that gained form.
Based on the lore about chakra, it is the life force of living things, a soul.
So basically the 10tails is just chakra without a body.
Any of the beasts are just chakra that does not have a body. Remember that the 10tails is just Kaguya's chakra and the Gedo Statue is her body.
That is why Madara did not awaken the RinneSharingan until he absorbed the God Tree as well (since it is what the Gedo Statue before it degenerated much like how chakra evolved into a beast).
That 10tails is someone's chakra. I mean, it could very well be Momoshiki's as he also became a complete being. Although I doubt that since his profile would've been updated and his forehead would have had the RinneSharingan.
It could be Isshiki's although we only know the requirements of 10tails from Kaguya so we cannot exactly say that it is his as we do not know whether or not he also became a full being (has both Yin and Yang). If he did, who did he consume?
It is possible that he ate a God Tree as well but that would mean that he would have become an enemy of the Clan as well as that is what Kaguya did (should the story be accurate).