In light of some of the relatively recent reveals I've started to entertain the possibility that Lancelot's Hazy Moon might fit the same template as Percival's Hope, perhaps due to both of them being hero-type. By that I mean that both of them appear to possess somewhat generic energy manipulation but with the addition of a unique twist. In Percival's case this is his hope empowerment gimmick that enables him to tap into his allies' emotions to buff himself, a very fitting power for the MC given how it grows stronger the more people he befriends over the course of the story. If Lancelot's magic were to include a twist of its own then its special property would likely be related to power output.
During the lake flashback we saw Lancelot fire a Shining Road at the Lady of the Lake, which depleted his magic reserves in one hit. This is very unusual since characters typically aren't able to channel their full magic reserves into a single attack, especially one that requires no preparation of any kind. You could maybe compare this to the limit that exists with something like electrical transmission, i.e. the thing that makes it so that charging your phone might take a couple of hours instead of a couple of seconds. It's just not feasible to transfer that much energy into the battery in such a short time. Similarly, even if someone like Escanor had enough total energy to create a hundred Cruel Suns in total, he'd still be limited to making them one by one instead of all at once.
I'm thinking that Hazy Moon's gimmick might allow Lancelot to bypass any such restrictions and simply pump as much energy as he wants into his attacks without the need to slowly charge them up. This would make the LotL's remark about how Shining Road will one day become stronger than the Sins' Nemesis combo quite a bit more reasonable, because it's not that hard to believe that Lancelot using up all of his magic reserves in one go could produce something more powerful that the total of the Sins' individual attacks that were used to form Nemesis, including the Full Counters that were used to boost it further. It's also easy to see why such a massive amount of power being channeled through an object practically in an instant would cause even ST-grade weapons to break from the strain, in a manner not too dissimilar to how an electrical wire can only withstand a certain level of current before the heat begins to damage it. Lancelot essentially needs an ST that has very high "magic capacity" (
https://en.wikipedia.org/wiki/Ampacity).
Aside from the appropriate weapon the other drawback is that using up all of his magic reserves in one go leaves Lancelot drained and barely able to even stand. This is an issue that was solved by him absorbing the LotL and her infinite magic reserves. Once he obtains an ST as well he should presumably be able to fire off Nemesis-level attacks at no cost to himself, which is a completely broken combination of abilities. It is for this reason that I expect Nakaba to give him the Ban treatment. If Ban had been allowed to retain his immortality after his Purgatory boost he would have become borderline unkillable since what little damage enemies could inflict on him would just instantly regenerate, in fact it would have also made him immune to Cath's time magic and presumably allowed him to solo the cat without needing the other Sins' help. That's why the first thing he did after returning from Purgatory was to give up the power of the Fountain of Youth. Nakaba simply couldn't have someone that overpowered as part of the main cast even in the endgame. Lancelot is very much following in his father's footsteps in this regard so we'll see how Nakaba decides to handle his case.
A relevant side question here is Lancelot's magic absorption. Some people believe this to be part of Hazy Moon but I'm more inclined to believe it comes from the LotL. We've seen the absorption be likened to water on multiple occasions now, which is a pretty obvious nod to the lake's power to absorb magic that was already established back in NnT. Nanashi even seemed to recognize the power upon seeing it, something that only makes sense if he had already seen or at least heard of it before. It would also be a strange coincidence for Lancelot to randomly end up with two identical abilities. Based on all of this I lean toward the idea that the magic absorption has to do with the LotL, though I will note that Hazy Moon being built around both emitting and absorbing magic would parallel the way Snatch can be used to both steal and give power so there could be something to gain from that option as well.
On a somewhat related note, I've seen claims that Hazy Moon is what allowed Lancelot to absorb the LotL and her infinite magic, but I don't believe that this is actually supported by anything in the manga. To begin with, there's nothing unusual about absorbing the lake's power given that we saw Jericho do it as well. The thing that made Lancelot special was not his ability to drink the water, but the fact that he was able to remain sane while doing so. This would suggest that it was a matter of mental strength, which is reinforced by the narration when Lancelot eventually decides to drink the entire lake:
Everything here points to Lancelot achieving his impossible feat due to his strong resolve rather than because he was simply born with the right magic. The parallel to Ban's Purgatory adventure is very relevant here considering how that too required incredible mental fortitude. It's what kept him from losing his sense of self and permanently remaining as the fox monster that he spent decades or centuries transformed into. His determination came from his love for Elaine and his bond with Meliodas, which should sound familiar. Like father like son. Also note that from a writing point of view it's pretty much always better for a hero's accomplishments to be the product of his efforts rather than mere blind luck.
As for Tristan, I'm sticking with my initial theory of Nova being a buff magic similar to Merlin's Infinity that is intended to be used alongside other techniques or spells rather than something standalone like Hope or Hazy Moon. Based on Heal Nova seemingly just being an extremely potent healing technique this idea seems to still be in the cards. It's less impressive than Percival and Lancelot's fancy hero-type magics, but it's important to keep in mind that Tristan has not one but two racial powers in addition to a fusion of both. That stuff adds so much to his arsenal that it's no surprise his innate magic would be made a little weaker to compensate, lest he become too overpowered. The Nephilim thing also seems to be the aspect that Nakaba wants to focus on the most when it comes to Tristan's abilities.
Gawain is not the topic of this thread but I'm actually more curious about her Dawn than either Hazy Moon or Nova. The reason why is because it currently just comes across as slightly different version of Sunshine. A rehash of an existing magic pales in comparison to the brand new and very distinct magics of the other KotA, which gives me the impression that there's more to Dawn that what meets the eye. An idea I really like has to do with its name. Dawn is when the light of the sun has only just begun to appear, which could imply that the magic is currently only in its infancy and will undergo further evolution in order to reach its full potential. This is in line with the new information we were given about magic abilities in this series:
Percival's magic seems to just be powering up over time and the same is likely the case for Lancelot and Tristan as well given that there would be no reason to refrain from properly revealing their magics for this long if they were going to turn into something different in the future. This leads me to believe that Gawain's magic could be the only one among the KotA which falls under the transformation category. The sun rises at dawn and peaks at noon so it would only be fitting for Dawn to eventually become Noon and develop strange new attributes, just like how Anne's magic went from allowing her to see lies to punishing liars with gravity.
Also, with how important of a character Galahad is likely going to be I sure hope Nakaba doesn't decide to keep his magic a secret for ages as well.