Haha, the length of that post is tame compared to what I used to write on my heydays.
I'm glad I can even post somewhat more regularly again since I had to forego forum activity for most of 2019 anyways.
It is obvious that the inclusion of Ven and also the other already known characters in the chi-era is to primarily generate interest and attention for Union X and get people to invest in it. Exploring eventual backstories and characterization comes secondary to that which is also shown with how utterly dragged out and disjointed the main story in Ux is.
Yea, but that's because character arcs are not really a priority for Nomura & co. First comes gameplay, second flashy gimmicks and "surprising twists" that even invalidate some former main plot points. Add to this now Nomura's salt and seeming obsession with Versus XIII and you get something that is steering off course for sure to what might have been planned when Days, Coded and BBS or even DDD were made.
The fact that it was established multiple times that Xehanort is quite interested in Ventus is probably the biggest factor hinting that there's more to Ven's past even if it got never center stage during the main plot except maybe in 0.2 when Terra warned Aqua about it.
With Ven's awakening station in BBS I was always skeptical because it showing the Keyblade Graveyard can also be because "this" Ventus was indeed created at the Keyblade Graveyard since it was the location where Xehanort did split his heart. Sora's station also looked different as a child than as a teenager and it is possible that a heart can have multiple stations after all.
Like said, considering how Ven is consistently portrayed it would be logical if his darkness is more based on fear, his own insecurity and maybe some traumatic stuff he experienced during the original X[chi] worldline where the audience never gets to see him, not aggressiveness, malice or outright evil intentions.
Sora's "messianic" role in KH 3 is still something made possible by the multitude of connections he forged and his conscious choice to follow them through. Anyone could do that if they were as determined as Sora, it's not something that's innate to him or being decreed by fate.
It's Sora's choices, not what he inherently is.
In Re:Mind it is also only stated that Ventus is "too pure" with no statement made about the light/darkness ratio in his heart. In the BBS reports Xehanort also calls Ven to be "too benign for his own good" before the split so it is also possible that it isn't about light/darkness at all but simply Ventus' core being without any element attached to it.
One has to remember that for example Spirit Dream Eater are also very friendly and helpful by devouring bad dreams, yet they're all made of Darkness.
Then again, Ven being a natural BWAHOPL (yep, I still remember this abomination of an abbreviation from 2011) would be a twist requiring new explanations and throw a wrench in the current established canon of the "only seven pure hearts" so I guess one could see it as exactly up Nomura's alley to pull. ;P
If it was really Ven doing it yea, it would require quite an explanation and finesse to make such a radical change believable in the first place.
Whatever entity hiding in him taking control however would be just a Terra => Terra-Xehanort situation or, more similar, like Ventus-Vanitas from Aqua's final battle in BBS.
Indeed, BBS was very explicit about that but it does not have to be the entire truth. It is possible that there can be more to it just like it was with the whole Nobodies have no hearts thing.
The notion was never really retconned but DDD revealed that Nobodies can gain a heart using procedures apart from the one way Xemnas was propagating throughout Days and KH 2. These other possibilities were deliberately kept secret though.
I wasn't around for a while so I can't really comment on "hostile" discussions about Ven.
From my experience discussions involving Vanitas tend to get heated with Ven only involved on the sidelines, but whatever. ;P
Pfft, yeah, he was also wrapped in a white blanket at first so I always took him being shirtless as symbolism for purity, innocence and/or vulnerability.
Not to mention this is four years before BBS proper so Ven is still 11/12 years old in that scene despite BBS not bothering to use younger models.
Funny, theorizing that Ven is the literal wind to scatter the Dandelions (or the wind the Dandelions will ride to a new world as Lady Ava herself stated in the original X[chi]) was something I did already back in 2016. I think I even started an own thread about that topic.
I'm not too good with remembering all the Ux stuff because it is released so disjointed, so what big clue you you mean?
I think it was the BBS novel which mentioned Ventus actually being an orphan who never even met his parents, but that's of course ambiguous in terms of canonity so unless a game gives a definitive answer fans can head canon what they want.
That he already swings a Keyblade this young is indeed an oddity we haven't seen anywhere else so far as most of the Keykids in X and Ux, including Blaine, Skuld and Ephemer seem to be between 14 and 16 in age so Ven definitely stands out with 11/12.
When it comes to Sora and Ventus I generally want to see more of them together in any possible forms. So far their supposed close heart connection wasn't really used to its potential.
A Heartless is created when a heart either succumbs to its own Darkness or is captured. In Ven's case however the Darkness was ripped out of his heart by Xehanort because he refused to use or access it in any form. Vanitas isn't a Heartless because of that alone.
As already said though, the possibility that he's more than "just" Ven's Darkness was there from the get-go, it just wasn't entertained by most fans and theorists.
The most irritating thing about Ven's statement is that he practically regressed into a mindset he already was over and which he regains one scene later when Sora joins the fray.
Even in BBS while acknowledging Vanitas came originally from him he never did view him only as an extension of himself running amok and he made it very clear he doesn't want to merge with him.
The new scene in Re:Mind is the only one were arguably both Ventus and Vanitas act OOC although Vanitas' is less facepalm worthy because him being more than just Ven's Darkness was always a possibility and it is also possible for him to have a sort of identity crisis because of different sets of memories affecting his heart.
When talking with Aqua at Mysterious Tower Ven hints at remembering different things through dreams but who knows if Vanitas has an equal "smooth" journey with different memory sets mixing?
It is possible that Vanitas has now some memories of Ux Ventus, some of a possible third entity and then on top also his own and if they all mix it can result in some weird behavior.
So your idea of Vanitas being a mix isn't that farfetched. No, I even think it is a very strong possibility not only because it would bring up further parallels between not only him and Roxas but also Xion and Naminé. It would bring the four "unnatural spawn offs" even more into one category despite the differences of their origins and would be consistent with the everything can grow a heart theme.
Same, more Sora/Ven and also Roxas/Ven interaction is what would make my day. The short interaction between Rox and Ven during the show down with the Norticas was already top notch, yet only another teaser so to speak. Sora in Ven's heart instead of vice-versa was also a great setup but it ultimately only served as a prop for another boss fight.
That's because easy plotlines don't fly with Nomura. It has to be elaborate, full of twists and "surprising", consistency or logic be damned. That's also why I said earlier to Twilight Lumiair that character arcs and relationships are not top priority for Nomura either. Making everything "surprising" is.