As an interesting observation, Majora's Mask seemed to start a pattern of having anything to do with death in Zelda games working on base four. (for Twilight Princess, anything to do with the twilight realm works in fours - four pieces of the mirror of twilight, four fragments of the fused shadow - while in the series as a whole everything to do with the living works in multiples of 3: the triforce, the 3 spiritual stones, 6 medallions, 3 flames of the goddesses, four fights against Demise, three living dragons the fourth of whom is dead when you find them, eight stops for the ghost ship, four dead bosses repeated beneath the waves - though apparently there were meant to be five until a dungeon got cut due to executive meddling).
Never would've picked up on the stages of grief, mind blown there, I had the whole theme of the game marked down as rejection so I was completely barking up the wrong tree. I'd even rationalised the four guardian marks as different elements of savagery - rejection of civilised values etc. will elaborate on request. Odolwa was barbarism, Goht was primal force, Gyorg was predation, Twin Mould was decay. (To indulge in a tangential topic for a moment, Twin Mould is a carrion worm. What do you imagine must've lived in that desert before it came along that was big enough for its corpse to let a carrion worm get THAT BIG!?) This interpretation kinda holds up on a superficial level - the masks represent a rejection of identity, time travel represents rejection of consequence and accountability (tends to do that in a lot of games, see Prince of Persia for example, excluding Two Thrones where they decided to chisel the analogy into an anvil and drop it on the player's head with that scene in the well) but your interpretation is actually built into the game's world itself and is present beyond a mechanical level so I'd agree it's probably what the developers were going for.
The masks seem to be more tied to tradition in several ancient cultures for funeral masks. I know in Egypt the mask was only ever worn by the deceased, but in some Roman funerals relatives would wear a mask of the deceased for the ceremony as if the deceased was still there. This seems to have a parallel with how Link uses the transformation masks to channel the spirits of the dead and he wears them in the presence of others who were close to the deceased but have not had the chance to say goodbye. Was there anything similar in east Asian cultural history? I would argue that the giant's mask and fierce deity mask be discounted from any list of transformation masks - they don't have the same uses, they are sorted differently in the inventory screen and are only available in boss battles - the masks may be made from the dead but they are a way to keep them anchored to the living and have more to do with life than death, therefore I must argue that there are three, not four or five. (I noticed you said four in the video, not sure if you meant the giant's mask or fierce deity mask as the fourth)
The only issue is tying in the time travel mechanic with these themes of death and grief. On the one hand, every time he uses it Link ends up back in clock town i.e. back in denial. Another way of looking at it is setting Link us as this godlike figure (fierce DEITY mask for instance?) who can overcome the inevitability of death. He doesn't have to face that fourth day like everyone else. By building him up in this manner it not only adds to the player's power fantasy but also adds credence to your interpretation of the Goron section - if Link is at an elevated position their bargaining makes more sense. (interpretation kind of breaks down if you consider that they think they're appealing to Darmani instead of Link)
As a parting note, I can't help but wonder if the ambiguity you noted concerning the Gorons was a case of the text being a victim of its own media form. People asking you to do stuff for them doesn't stand out in a video game as much as it should because all the NPCs do it all the time. XD
Great to see you doing more of this, brilliant work.
Edit: Now here's something interesting - if Majora is linked to death, why does his battle have 3 stages?
