A lot of what I wanted to say has been covered so I'm just gonna focus a sec on one thing I've been thinking about lately.
Addressing Xemnas' connection to Terra, Ven, and Aqua.
I was bound to talk about Mansex eventually.
But....out of everyone, his character was shafted to most.
His talking with Aqua's armor was originally a big deal, but was never touched upon afterwards. That one scene in 0.2 where Xehanort is talking with Aqua maaaay have something to do with it, but I just don't see it, nothing was said in interviews or the Ultimania, and this is a case where "because darkness" is actually a better reason for once.
In Days, Xemnas gave Roxas a pat on the shoulder. This was meant to show his connection with Terra, as Terra did the same with Ven in the BBS beta trailer, but was removed in the final version. So now it means nothing.
Xemnas' "So, sleep has taken you again." toward a comatosed Roxas was a pretty damn important line, again showing his Terra side, but was cut from the 1.5 Remix scenes. Xemnas also wanted to find the Chamber of Waking in order to find his other "friend" (Ven), yet he has no involvement with Castle Oblivion/Land of Departure in KH3.
These bits from Xemnas showed there was something more to his character, but nothing came from it. Instead of these things being addressed, Xemnas just exists in KH3 because he's expected to be and look pretty.
I always found it interesting on just how much Terra and Xehanort he might be, especially when you consider that he could have been in the same boat as Roxas and had been a zombie upon creation as, since Sora getting his memories back caused Roxas' lack thereof, Ansem having the apprentice's memories would theoretically mean Xemnas didn't. So what he does know from his apprentice days would be from memory leaks (like those things Roxas had) or being told by others. Because of the complete mess his creation was, he has muscle memory and vague memories from Terra (and I guess Xehanort too.)
So I doubt something like the DLC would address something like this considering the amount of attention it would need and how Nomura seems to just not want to do it given how it's never touched on at all in the base game. I'm still bummed Xemnas didn't get any interaction with TVA.
And now he's dead.