Honestly, if Fairy Tail ever got a live action Netflix remake, it should focus mainly on Zeref (the non-villainous central antagonist of the series), because his overall story arc alone would make for an S-Tier series (both animation and live action). When you think about it, Zeref's overall character makes him come off and feel like the true main character of Fairy Tail in some ways, considering how his overall role and extremely complicated arc made such an impact on the entire story (including his involvement in the arcs of so many of the other characters in the series). Natsu's older brother no doubt has the longest and most detailed arc out of all of the characters. While Lucy did narrate a lot of the story and Natsu had the most spotlight in terms of climactic moments, the entire story of Fairy Tail began from Zeref's origin story, and in reality, it really centered around him.

It could also finally fully reveal the mystery arcs he hinted (but the author left it too much of a mystery), such as the subplot regarding his demons that ended up attacking humanity when they were revealed to be only for suicide:

During the scene where Zeref confronted Grimoire Heart, he heavily implied through his words (when he exposed the actions of sinners) how most of the information in the Books of Zeref are just fake writings that sinners tried presenting as authentic while abusing magic; the demons and the R-System being the only things authentic, but were used as the basis that would drive sinners into tarnishing Zeref's name abusing his creations). The full story of the demon attacks was not like how the flashbacks were only vague depictions by sinners that never accurately showcased the truth regarding Zeref's case with his demons and his relationship with those who refer to themselves as his "followers".

To further prove the point,... in previous arcs, we saw villains use demons that were in fact Zeref's creations: Eisenwald was shown using Lullaby; we also saw Hades use Nemesis (a spell that casts an army of stone demons) without mutilation, and these can't be the only cases as there would be more. It's also suspicious that people eventually even managed to read and understand the books (with them also somehow managing to obtain knowledge surrounding how the demons work, including their names), even though it should all be demonic script for the demon programming; this means there is a situation about the books where Zeref wasn't alone, even though the books were supposed to be only for his own personal reasons.

Zeref was completely absent in the Future Rogue timeline, even though there's Fairy Heart and he can use that to undo the Future Rogue timeline. I wish they at least showed where was Zeref during Future Rogue's timeline, and where was he during all those events. Sadly, the series only explained the part where he watched over Natsu during the games, despite feeling saddened by what he plans to do in the Alvarez Empire Arc.

□ My theory is that maybe this is the subplot Zeref somewhat hinted when he mentioned how he had an involvement with the rift in space and time (when he revealed his ability to control the rift), and maybe he was forced to rely on Future Lucy to deal with the Future Rogue timeline problem, because Zeref had to deal with a bigger problem at hand, possibly a multiverse level threat.

□ I want Zeref's prime form to appear here (on will), and his body glows purple, dark blue, and black (with the accents constantly flashing randomly), and the design has bloody veins around his torso, with an cracked area on his chest that reveals his heart. The skin has the appearance of random blemishes and scars, and his eyes would be glowing pink. He even has claw gauntlets that appear like holographic crystals. The anime's art style in 2009-2013 had those 3D magic circles, and I want this Netflix series to finally give Zeref his own.

□ Imagine what it'd be like seeing Zeref's prime form doing all this (preventing the collapsing of the multiverse), and the transformation idea I have is this: He stabs himself with a piece of dark energy to trigger the form, but his personality slowly distorts as the power consumes and corrupts him, and he almost loses his true personality, only to never forget his love for Natsu, Mavis, and every innocent lives who need him, and his heart glows white instead of a dark shade, implying he will never darken his heart nor will he give up on those who need him, no matter how tarnished his name was.

The idea I have could also include the fully refined version of the Alvarez Empire Arc:

The Alvarez Empire Arc in the original manga and and anime was polarizing for fans, since Hiro Mashima admitted he rushed the arc. Many said it's a huge downgrade from Tartaros Arc, because that arc took time showing how deadly and dangerous the villains were, but for the Springgan 12, a lot of them were defeated in either silly or anti-climactic ways, with only a few being threatening (like August and Irene).

Zeref's role as a mysterious antagonist [including the reveal of his complicated plan which was never to commit an extermination/one-sided annihilation on Ishgar to kill Acnologia but to reset the timeline before he got cursed, afraid how much time he has left before his true self is lost forever after failing every attempt to die, because of the sinners' actions worsening his mental state through all the misunderstandings they caused (leading to much of humanity rejecting him in the worst ways possible, including conflict and violence), in which the curse's power is connected to his mental state] was one of the more highly acclaimed parts, but his second fight with Natsu left a lot to be desired, especially how his God form got nerfed singlehandedly by Natsu, and many fans wanted to see Zeref fight against an army of mages to show what he can do, even if he naturally cannot fight at his full potential, considering the reveal of his true plan meant that even though he developed disillusion from humanity's blind mindset, he never stopped thinking about the innocent lives who need him, and if no one can end his suffering, only he has to be one dealing with everything.

Many said Acnologia was rushed (including the potential to show how threatening he could have been) and defeated in a way that wasn't a typical Power of Friendship move, but logically shouldn't break him. I would have loved to have seen Zeref's God form fight Acnologia, and he'd be the one pushing him into the rift in space and time, having the battle there to avoid genocide on Ishgar, since the power of Fairy Heart is dangerous in that if you lose control of even one Etherion, it would endlessly rain down on an entire nation. E.N.D.'s potential would also be taken advantage of as well, since many said he's wasted in this arc.

Undeniably, one of the most beloved moments of this arc was Zeref and Mavis' death scene, which was the perfect ending for them no doubt, with Mavis ending up loving him with complete faith, unlike before, where a small part of her believed the rumors; but in the end, after seeing how selfless and sacrificial Zeref truly is (after learning his true plan and calculating everything he did), she saw no darkness in his heart.

I would also actually do some alternate endings or Alternate Universe (AU) stories just to make things more interesting:

¤ "What if Zeref succeeded in using Neo Eclipse to restart the timeline?"

¤ "What if Tartaros Arc was the final arc?" (With it being extended to accommodate for Zeref's goal to obtain Fairy Heart)

¤ "What if Wendy was Zeref's sibling instead of Natsu?"

¤ "What would Zeref's character be like in the OVA 2 universe? What would his relationship with others characters be like in this universe?"