Yes. The Otsutsuki clan has a significant presence in the Naruto series. Their power and mystery have intrigued many fans. Fanfictions exploring Naruto's connection to the Otsutsuki often attract attention as they can offer new and exciting storylines. For example, some might imagine Naruto having special powers related to the Otsutsuki, or different interactions with Otsutsuki characters that were not in the original series.
One possible plot could be that Naruto discovers he has Otsutsuki blood in him. This could lead to him having new and uncontrollable powers that he has to learn to master. He might be shunned by some in Konoha who fear his newfound abilities, while others see it as an opportunity for Konoha to become even stronger. Naruto would then have to struggle with his identity and prove that he is still the same Naruto they know and love.
Yes, it can be quite popular. Many Naruto fans are intrigued by the idea of Naruto having such an extraordinary lineage as being the son of Kaguya Otsutsuki. It adds a whole new layer of depth and mystery to his character, allowing for different interpretations of his powers and his place in the Naruto universe.
One great 'Naruto Momoshiki Otsutsuki fanfiction' is 'The Otsutsuki's Ascent'. It delves deep into Momoshiki's backstory and his interactions with the Naruto universe in a really interesting way.
Power is a common theme. Since Momoshiki is such a powerful character, many fanfictions explore how his power affects the Naruto world and the characters in it.
One idea could be a story where an Otsutsuki member infiltrates the Akatsuki. They could have their own secret motives that conflict with the Akatsuki's goals, like using the Akatsuki as a tool to gather more chakra for their own clan's needs. Another plot could be about a young Naruto being mentored by an Otsutsuki in secret, and how this affects his relationship with the Akatsuki later on. Maybe he tries to persuade them to change their ways using the knowledge he got from the Otsutsuki.
If you combined Naruto's determination and power - up abilities with the Otsutsuki's unique dojutsu and chakra - related powers, and then added the Akatsuki's knowledge of various jutsu and their strategic thinking, it would be an extremely powerful character. Naruto already has the Nine - Tails' chakra and his Sage Mode. The Otsutsuki have things like the Rinnegan. And the Akatsuki members are no slouches in combat either. So this combined character would be able to take on just about any foe.
One interesting plot twist could be that Naruto has hidden powers that are only awakened when he discovers his true heritage as Kaguya's son. These powers could be something completely different from what he already has, like the ability to control space - time in a unique way.
It's hard to say for sure. Both Ichigo and Naruto are incredibly powerful in their own ways, and it would depend on various factors like their current power levels and the circumstances of the battle.