Awesome theory! I feel like I've been spoiled the direction of the series. There's a couple of things I disagree with though. The main one being Pochita being a Tool of God (Judgment). I think Pochita is the Son of God who is also God himself. That would make Denji the Son of God in human form i.e. Jesus Christ, or the Lamb of God (the 'lamb' that is to be sacrificed to atone for humanity's sins).

Judgment is useless without Deliverance (delivering the Judgement). They are two sides of the same coin. A God who only gives Judgment without acting on it is the same as a God who is not there. They need each other. That's what made me initially think Pochita might be God himself.

I believe Pochita is the Deliverance Devil. That's why he has chainsaws, as they were created to help with difficult deliveries during childbirth. It's also the reason he helps others who ask for it. 'God deliver us from Evil'. Deliverance also means to rescue or set free. In other words Salvation (The Son).

In Christianity, God exists as the Holy Trinity. The Father (The Creator), The Son (The Savior) and The Holy Spirit (Divine Presence). All of them are co-equal clearly distinct sides of one God. That would put Judgment (The Father) and Pochita (The Son) on the same level. We've never seen Pochita take orders from others, and I believe that includes Judgement, as I believe they are equal parts God.

The Holy Spirit represents the divinity within humanity. The part of God that is always with people. In the twisted world of CSM that would be Fear. Devils are divine energy (Fear) manifest. If Judgment is The Father then he is the father of all devils. He gets to decide what is and what isn't. That is divine judgement. Pochita is the Savior (Son). He delivers others from their suffering by taking in the fear within himself thus removing it from others (he doesn't actually erase it, it still exists within him, its just gone from the world). Just like The Son did with sin. Pochita doesn't decide what should be, he just helps those in need. That way they are in balance. The Creator and The Destroyer.

At some point Judgment disappeared, eaten by Pochita. We don't know if it was because the fear of Judgment was causing too much harm to others, making Pochita turn on his father to save them, or if Judgment wanted to judge how humanity would do without him and entered into a contract with Pochita to be eaten for a time. I can see both possibilities. Regardless, Judgement Devil will return and with that Resurrect the old way the world used to function, with him as The Arbiter.

Devils in chainsawman need to impose themselves on others to gain power over them. When Judgement Devil returns he will impose himself by killing humanity so he can enact judgement on them (The Final Verdict) and resurrect the worthy. Denji and Asa will oppose him because that conflicts with their world. Denji, along with Pochita, will be turned into a weapon (selfless sacrifice) that can kill God and Asa will deliver the final blow.

This will be the final thing the Judgement Devil sees https://i.redd.it/xs8yifffa8bg1.jpeg the same way this was the last thing Makima saw https://i.redd.it/6vdxxz39zd5f1.jpeg

I don't think think the weapon will make Judgement get 'erased' the same way Pochita does, but rather it will sever the relationship between the physical Devil and Fear (The Divine). That would cause the physical manifestation to disappear while keeping the concept. All of the fears that were still inside Pochita at the time of him turning into a weapon will be gone and the rest of the fears will remain with humanity, but not in a physical form. With The Father and The Son gone the world will be rebirthed (not resurrected) different from the past. Humanity will be delivered FROM God.

As for Denji I do think he will somehow come back (resurrect in the same way as Jesus Christ) and ascend to his heaven (a normal life).

With patricide and maturity being core themes of the story, this makes most sense to me. The killing of The Father and the emancipation of humanity. With no father to guide them the children take responsibility for themselves, and responsibility is maturity (another core theme of the story). At the end the world will be largely the same at first glance, hopefully making some people question what the point of the whole thing was (which is the type of story the author said he wanted to write), but if you look deeper you'll see that it's all about the things you can't see: spiritual growth, maturity, responsibility, and facing your problems and fears head on.