Mythology explains that Madara and Hashirama are personifications of Mara and Buddha whereas the concepts of Will of Fire and Curse of Hatred are an allegory for reincarnation.
Buddha preached comprehention, love and enlightenment no matter how hard reality seemed to be because all pain and hatred are illusions and temptations which must be overcome.
Mara's goal is for all beings to stop moving foward and live eternally in the realm of pleasure. To give up truth in the face of illusion.
Buddha was always hailed as a saviour and idol to be followed, yet he himself never cared for power or fame and simply wished for people to understand his teachings rather than build monuments and wage wars in his name. Just like how Buddha could not stop humanity from remaining ignorant and hateful, Hashirama failed to create true peace in the world.
Mara on the other hand was loathed and dreaded by the people, he never defeated Buddha yet wished to have his power and place for he considered the struggle for enlightenment to be futile and did not comprehend why he was hated and Buddha was loved. Just like Mara, Madara (whose name is an obvious reference to the former) always lost to Hashirama, never understood the meaning of their struggle and had to resort to lies and temptations for people to follow him.
It's of important note that Buddha never saw Mara as an enemy, he always considered the latter a friend regardless of his actions, for true enlightenment holds no place for hatred or mistrust.
What's going on now is that Madara played cosmic houdini and stole Hashirama's power whilist Naruto has become the new incarnation of Buddha who must guide humanity foward to enlightenment while saving it from Madara's goal of eternally trapping them under his illusionary realm of bliss.
The Sage of the Six Paths is the representation of enlightenment, the ascended Buddha who Mara and his disciples try to emulate in their quest of power over humanity.
The Shinju represents the Samsara, irrational illusions which keep humanity tied to the cycle of reincarnation and suffering that must be overcome for one to become an enlightened being. The reason why it wants to assimilate all chakra back to itself alludes to how the Samsara has no will of it's own but seeks to trap all beings under it's ignorant control.
Hashirama, who had power over wood, the element of the Shinju, and who could peacefully subdue any of the tailed beast (the different stages of the Samsara), represented someone who had conquered irrational hatred and moved the world foward to a better and more enlightened arrangement.
Madara and his disciple Obito accessed the power of Hashirama to conquer the Samsara but like how Mara, despite being the strongest Deva second only to a true Buddha, could not attain true enlightment because his power and position illuded him from his flaws, neither Madara or Obito fully conquered the power of the Juubi to become like Hagoromo Ootsutsuki.
Obito, being a lesser deva of Mara, could barely conquer half of the Shinju (Samsara) whilist a huge deal of it's power (Eight-Tails and two Nine-Tails) still eluded his conflicted mind.
Madara, being Mara itself and the strongest of all Devas, conquered more than 85% of the Shinju (Samsara) whilist his strong but closed mindset eluded him the final step toward the full power of Hagoromo.
Naruto, the Buddha who instead of trying to conquer the Samsara through power conquered all of it's steps (every tailed beast) through love is the current successor of the true ascended Buddha. The reason the Shinju feared Naruto is because, like Hagoro, he seeks to vanquish it forever like how a true Buddha seeks to vanquish all primordial irrationality.
Another important thing to note is that while Mara and Buddha can be considered opposing forces despite not being enemies, neither of them can be considered good or evil.
While Buddha does his best to lead humanity towards enlightenment with his teachings, that path requires people to confront very harsh aspects of reality and more often than not humans fail to overcome their flaws and find themselves carried to a lower existence because they fall to temptation. Obito and Nagato both started as potential Buddhas but they succumbed to temptation and became Maras following in Madara's footsteps.
Mara on the other hand just wants all creatures to cease trying to find enlightenment and live in eternal bliss under the realm of pleasure, the strongest of all illusions. While some would find appaling to castrate humanity of it's potential to grow, the exange of freedom for pleasure could mean a much better existence for inferior beings who would have to endure much more suffering before attaining true enlightenment.
Last of notice is that the Samsara is eternal and that while one may attain enlightment during a life, they can, like how Naruto said, either rise or fall depending on the choices they make on the next one. Hagoromo (the first true Buddha) knew that it was only a matter of time before the Juubi was revived and that someone would either rise to defeat it again or use it's power to bring the world to it's knees.
The prophecy said the the choosen one would either bring a revolution or haze down the world and this alludes to how a few diffent choices can turn Buddha into Mara and Mara into Buddha.
Obito's hallucinations showed that had him overcome the temptation of reviving Rin and remained on the path of enlightenment, he could have accomplished what Naruto is trying to do now instead of trying to usurp Madara's place on the path of Mara.
This is to highlight that all roles in Naruto could have been reversed.
Hashirama instead of Madara could have given up on Konoha and he would be the one trying to subjulgate the world now.
Jiraya instead of Orochimaru could have given up on human strenght and twisted himself in the search of an immortal and all knowing existence.
Kakashi instead of Obito could have refused to accept Rin's death and would have manipulated the world into the chaos of war to bring her back.
More highlighted than anything, Naruto instead of Sasuke could have been the one trying to either burn down or control Konoha in revenge over the village's sins against him.
It is a good theory but there is basci difference between Buddhism and what Naruto wants. Buddhism is against wordly pleasures and both Hashirama and Naruto are somewhat vain, silly and pervert. They don't care at all if people surrender to temptation, in fact, there is no conception of temptation for them.
We can't deny however that the Rin'negan is the Samsara, it is explicit, the six paths not the tailed beasts are the realms of samsara. So there is hinduism and buddhism there, of course, Hashirama's summon is a clear sign but I would not relate Hashirama/Naruto/Jiraiya/Kakashi to Buddhism in any way, they love every wordly pleasure that buddhism consider a temptation.
As eastern story with western appeal Naruto mixes shintoism, hinduism and others with jewish-chistianism so Naruto can be Buddah as much as Jesus or any other myth hero. I would say Naruto is an archetype that we've seen a thousand times through many ancient and modern myth, like Neo from the Matrix.
Very interesting in my opinion. Thumbs up for the effort!!
Hagoromo Ootsutsuki was the only person in history to truly master the Rinnegan and seal the complete Juubi whitin himself. Thus he can be considered the Buddha of the Naruto world for completely conquering the primordial irrationality which keep humans trapped in conflict and despair.
The Tailed Beasts represent the 10 perfections of Buddhism that a person must practice to overcome the Samsara (Shinju).
While there maybe 9 official Tailed Beasts, the truth is that there is ten if you count each half of Kurama as individuals.
So far the 10 tails of the Shinju were divided into nine beasts that later became ten and all of them recognize Naruto as their true virtuous guardian.
Madara could only master 9 of the 10 because he lacks kindness and as such he cannot become a full Hagoromo.
As for Naruto and Hashirama having quirks and flaws negative to a Buddhist view, we must bear in mind that symbolism doesn't equal complete fidelity to the source of this symbol.
Instead of treating the cycle of reincarnation and Karma as something mainly spiritual, the world of Naruto treats us to the cycle of hatred with generations of humanity struggling to find peace.
In the place of negative Karma, we have hatred which twists people and leads them to war.
In the place of positive Karma we have the Will of Fire and it's similaries which allude to the never ending quest for achieving and protecting real peace.
As such, Hashirama's and Naruto's mundane flaws don't impact on their quest for enlightenment as their qualities working towards peace are much more proeminent.