Capitano possible return

So,

Capitano merged with the LotN to change natlan rules (to accept his comrades soul) and left his body to enter the night kingdom doing his work

The souls of humans who enter the night kingdom are technically alive (look at Xbalanque), but can't reincarnate until having a proper body (or possessing another body) via the ode of resurrection

Saduiga in the end of the AQ said some interesting lines :

Sadigua: The second hero is also an outlander.

 Sadigua: Many years ago, he forged a connection with this land and used his body as a vessel for the souls of his fallen comrades. 

Sadigua: His goal was to give them a home and, with that, a chance to be reborn into this world.

maybe he wants to be reborn in a new body from the stories recorded in the NKingdom, without the weight of his comrade and the burden of rot, erosion and the curse.

The blazing flint are offered to capitano, not to the throne, Blazing today, aren't we?

and capi is freezing between life and death

Maybe the flint are used to give it to the LotN, ooooorrr, to reawaken capitano via unfreezing his body and/or removing the rot in 5.5 (lansan tribe)or 5.6.

Surprisingly, one these patches feature the interlude quest

Also, in the last summer event, in the quest of the 3 blocky dudes that wanted to find the real record of defeating the dragon (each one claimed that his clan did), we were trapped in a throne unable to stand up, only after the 3rd time we were able to leave.

3 times to stand up : 3 patches to reawaken -----> 5.6

also we were warned to not sit on that sticky throne, just like capitano who was warned to not risk his life to mavuika

Also, Tsartista seems to keep capitano position as is ... secretly (the mondstadt couple said they heard whispers, not an announcement). Maybe he informed her about his plan and she accepted, restoring the prime power of her strongest follower (who is currently as strong as the pyro gnosis) is more beneficial than returning with the pyro gnosis (fighting for a 2nd time for the gnosis isn't not honorable) after all.

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Summary

Capitano main goal was to deliver his comrades souls, make a new body for himself from the story recorded in the night kingdom and then reborn (reborn mean to be be born again, in another body but with the same soul) with a healthy prime body, then start using his heart to get stronger and more powerful. All of this is to prepare himself to the initiation of project stuzha in the future.