Have any reputable philosophers considered this concept? If so, which ones? And how did they account for responsibility and accountability in their frameworks?
There's actually some discussion of this, believe it or not, in the Bible. Psalm 8 describes the exalted status of human beings, and Jesus in John 10:34 quotes Psalm 86's "You are gods" --although it's ambiguous whether either the Psalm or Jesus' invocation of it are meant to refer to (ordinary) human beings. When you come right down to it, the entire Christian religion is about God manifesting in the form of a human being.
Outside of a traditional religious context, some of the atheist existentialists considered human beings to be godlike in their command over their own destinies. I'm thinking here in particular of Sartre and Nietzsche. The secular humanist movement is sometimes described as making a god out of human beings (although chiefly by its detractors).
In the Christian context, an ordinary human being is still accountable and responsible to (capital 'G') God. In existential atheism, each individual is considered fully responsible for the entire world he or she lives in.
Consider the following 2 statements made by 2 saints at different times in different places.
Jesus replied, “If I glorify myself, my glory means nothing. My Father, whom you claim as your God, is the one who glorifies me. Though you do not know him, I know him. If I said I did not, I would be a liar like you, but I do know him and keep his word. Your father Abraham rejoiced at the thought of seeing my day; he saw it and was glad.” “You are not yet fifty years old,” the Jews said to him, “and you have seen Abraham!” “I tell you the truth,” Jesus answered, “before Abraham was born, I am!” (John 8:49-58)
मां च योऽव्यभिचारेण भक्ितयोगेन सेवते।
स गुणान्समतीत्यैतान् ब्रह्मभूयाय कल्पते।।14.26।।
Whosoever serves Me alone with an unfailing devotion-Yoga, he, transcending these Strands, turns to be the Brahman.
इमं विवस्वते योगं प्रोक्तवानहमव्ययम्।
विवस्वान् मनवे प्राह मनुरिक्ष्वाकवेऽब्रवीत्।।4.1।।
The Blessed Lord said I imparted this imperishable Yoga to Vivasvan, Vivasvan taught this to Manu, and Manu transmitted this to Iksavaku.
(Manu and Iksavaku appeared on the Earth long ago before Krishna took birth on the Earth)
We have to understand that uttering of these words, though apparently quite confusing and egoistic, can be stated only by the persons, who attained highest state of SPIRITUALITY.
In Spiritual realm, there is a method of disciple meditating on his own GURU (TEACHER), who reached highest level in SPIRITUALITY, treating the latter as GOD.
The 4 mahavakyas (great statements) from the 4 Vedas are different variations on the unity of atma (roughly soul) with Brahma (v v roughly God).
The second is particularly iffy because Brahma (often spelt in English brahman to suggest neuter gender) is a more abstract principle than the Judeo-Christian YHWH.
I have just hit on this idea as well OP.
After admittedly limited research I have yet to see any references to philosophy based on humanity's divinity outside of this thread.
It seems like an interesting framework to provide people with a sense of responsibility for their surroundings and as caretakers of the greater world.
If we worship ourselves then we can't pass the buck on to the will of something greater. We have only our own problems to solve. We are accountable to not just ourselves, but to that which we are stewards of.