Kelly Marie Tran throws out the ceremonial first pitch at the PETCO Park on August 20, 2022 in San Diego, California

I'm not pretty sure about the curse part for me too. But I like the idea of it. Although imagine Elizabeth brainwashing him to think he is in love with her so he could stay and betray the demon race for her. Her loyal servant I guess. Elizabeth acts like she loves Meliodas when there is public and private (Gloxinia and Drole doesn't know) so Meliodas won't get suspicious and finds out (She fears when he finds out he will be pretending to follow her in order to find away to escape from her or kill her when she is off guard.

Everytime Meliodas almost gets control again, he often has headaches and remembering the true event of what had happened during the past. Maybe remembering that he never truly love her and that it's all just fake? and when Elizabeth realizes what is happening she is refreshing the spell That's just my idea

The curse one... Yeah... Perhaps the supreme deity and demon king cursed the other one with the exact same curse but Elizabeth remembers everything every time she is reincarnated. Since the supreme deity was apart from this plan

Not sure, this idea is great but there will be some things to work on. And we both agreed on that.

I can imagine the way that the brainwashing works as you described, with Eli brainwashing him to think he's in love with her. Since she goes along with the plan of her mother though, I can imagine that she doesn't just not love him, but full on hates him and she might get annoyed with his lovey-dovey behaviour once in while and flip out. Not everyone can keep up a facade indefinitely, after all. Does the spell weaken when Mel dies and gets revived btw? Since the curse seems to restore his body and his emotions get taken away, wouldn't Elis spell be affected as well?

With the plan being to eradicate the demon race, I can imagine Eli telling Meliodas as soon as possible that to break the curse, they have to kill the demon king, and maybe the other demons, too, since the entire race will no doubt want to murder her (Eli) and Mel, who is so in love with her that he can't think straight (thanks to the brainwashing), agrees with her.

If Mel ever acts weirdly out of character for the brainwashing, Eli would probably lay it on again extra thick, regardless of when she did it last. She may have been a match for him during holy war times, but reincarnated, she likely isn't, or not as much. Plus, she knows how smart he is, she knows full well that he's capable of tricking her and killing her in her sleep, should he ever break free.

I don't about Eli always having her memories the moment she's reincarnated... Maybe instead of having only three days once her memories are restored, she gets longer? Or the death part of the curse would only become activated once Mel found out that her memories came back. Or something like that, but I'm not entirely opposed to what you said. Or maybe Eli does have all her memories the moment she's reincarnated, but she doesn't have the strength to brainwash Mel until idk, until she's an adult? Or she has to train her strength up again. Something like that, maybe? That would require her to have to rely on her acting skills more when the spell weakens, having to act more lovey dovey to prevent Mel from being suspicious.

Also, since Elizabeth goes along with the SDs plan, she must look down on the demons, but does she also look down on the other races? Also, does Elizabeth reveal to the humans that she's a goddess? Since goddesses are worshipped by humans and all, and she doesn't exactly have to fear being kidnapped, not bc she's a goddess, but bc of Mel essentially acting like a guard dog to her. It might give her an advantage, but it would also be kind of cruel, in my opinion. Which isn't to say that I don't like the idea, but it would go a little more into ooc (out of character) range with Elizabeth, and I don't know if/how much you like the idea.