... but overall this fits potentially so well and also has so many great story tie-ins over a truely "new" character. Meanwhile with Harald we already have all the motive, the potential burn scar explanation, the connections to the story right now and a huge tragic/wholesome potential for redemption

- while the event has been described as the day "King Harald" died, I can see this fit a metaphorical death in his role as king and insted becoming the rumored mysterious outlaw, who is waiting for the right pirate to come along to challenge the very WG that betrayed him.

Or it's someone else ...

-Gaban could also know and him wanting to talk to Luffy again later might have been him trying to send Luffy Harald's way as someone Harald has been waiting for to allow the poneglyph to go to
-Harald leaving Elbaf ashamed and hiding away as a ghost on the seas would fit with his regrets
...

-storywise him wanting to die but instead having to live with all of his regrets and the fallout of his choices would be fittingly tragic
-on the other side Loki lying/covering for Harald living would mirror Shirahoshi's lie for Otohime and as Mosa is likely her, it's an interesting parallel
...

-so him not dying but losing the mark by it being burned could make sense as we also see Shanks lose his mark by losing the arm
- a WG enslaving mark being burned over setting someone "free" would also tie beautifully back to the Sun Pirates (and we just saw Fishe Tiger in the flashback again)
...

-he worked for the WG which fits the rumor Shiryu had heard
-Saul, Vegapunk and Gaban have all been on Elbaf and are knowledgable about some of the poneglyph stuff they could have shared with Harald
-he was made "immortal" by Imu and asked Loki who we've seen produce lightning/fire to kill him
...

...that he is sorry but a very special lady is waiting for him already.
And then next we see him get back to his room above the restaurant and it turns out his little daughter is waiting for him excitedly and he hands her some ridiculously elaborately decorated unicorn cupcake.

And I think that's at the very core of the message here: it is a system that is inherently inhumane and thus even oppresses and harms many of the people that are inside of it.
When being a marine makes it harder for people to actually be good and do good, then the whole system is the problem.

...is that this is what we mostly see for marines in the story. Many of them actually want to help people and because the Strawhats do that while their orders prevent it, they disobey/overlook orders at least for the moment.
Kizaru didn't and because of that he killed a friend and it hurts him...

Given that it happens after Loki jumped down to underworld and had his "I can't even die" moment, I actually always took it as a Rocks "covering up" his injuries from that. Now when Harald asks about Loki's injuries, he got them from the rowdy strong pirate in a fight and not from trying to die.

...It feels like it is more and more common to see silence, neutrality and lack of opposition as being ultimately complicit in what you are failing to openly oppose and Garp seems very symbolic for that sentiment in One Piece and now might almost be a timely symbol for people's overall frustration.

... has more to do with the larger current "Zeitgeist" throughout the world?

I feel people at large might be more criticial of silent opposition or "lackluster neutrality" (in lack of a better term) and are starting to demand more open opposition from anyone that is in a position to do so. ...

...stands against the system, but looking the other way when Dragon/Luffy/Roger are doing it and letting them get away with it, is as far as he will go.

...when he is talking to Garp after turning himself in that he is gonna do something about Ace, because hiding a kid from the WG by entrusting it to the other, is what the two of them already did on God Valley once.

It's just the type of thing that would feels very Garp to me. He never openly ...

...and then Garp is aware that pirates looting a treasure chest is gonna be the one way to get something off the island without the WG getting involved, so he is letting Roger get away with that specific chest. And I think Roger understands that after opening the chest. Which is why he is so sure...

I actually have a bit of a suspicion that Garp is gonna be the reason Shanks ends up with Roger as he seems like the perfect connection between Dragon and Roger.
I can very much see a scenario where Dragon is pleading with Garp to save the kids as he himself doesn't have the standing ...

... a price to be claimed in a bullshit tournament and then she goes and finds Rayleigh because he has always been her choice and none of what happens on God Valley is actually relevant to her chosing him.

As another option I'll also take Gloriosa saving her and getting some Kuja duo moment.

With how obsessed he is with 3s I figure everytime he goes for squares it becomes a triangle because "3 pointy things" is what he instinctively gravitates to.