Fantastic FAQ, answers a lot of my first doubts.

Gosh, this looks so complicated. On the one hand, kudos for PSO2 Meseta maintaining the original game intact so there will not be a riot over changes people don't like. However on the other hand, since they are remaking base PSO2 visuals anyhow, I wish they would only go 100% and synchronize personality versions entirely. Giving old players some free style items and unlocks will be sufficient to bribe everyone to take the new system.

Synchronizing 100% character models does not sound easy. The dilemma is that the old outfits and layer use are modeled to match the older pso2 body. That is not likely to happen. I mean that I'd be willing to drop a certain proportion of those cosmetics to keep things intact across variations. Provided that there's a steady feed of cool new things to replace it, I do not mind. I constantly rotate out my old looks anyway. As long as the character versions translate 1:1 it will still feel like mine.

I'd envision a massive complication to this involves a lot of the makeup from the Western side of things which were exclusive to collaborations, promotional events, and events that no longer exist. The example I can think of is the Monster Hunter Frontier Z collaboration where I could imagine the clothes and weapons could unquestionably be given a visual upgrade together with everything else but I don't exactly know how the licensing or the way the legal side of the cooperation works where I'd wish it was as easy as Sega going through and upgrading the assets but I do not understand about just how much of Capcom is involved in that process.

The same applies to collaborations such as the Final Fantasy XIV collaboration with Odin (which still exists as far as I know) where I don't know just how much Square Enix is involved in that for Sega to have the ability to upgrade assets . If it was only just Phantasy Star-related things (like character outfits, cameos from different games, or alternative Sega-related properties) I could envision that this likely would have been done, or would be done. But from the Global version we already don't have the presence of Cougar NX so that I don't know if there are additional complications regarding Sega's own properties that might also contribute to not upgrading everything they could within reason.

I can imagine that probably out there we will still see someone wearing those old collaboration items even if they are not rigged up to cheap meseta pso2
the very same standards as new cosmetics in a similar way and that there definitely would have been outrage when it had been made obsolete or unusable. Collabs who've experienced their cosmetics removed still have their resources exist on the game so those will probably still be accessible for jp players.