Gosh, this looks so complex. On the one hand, kudos for keeping the original game intact so there won't be a riot over changes people don't like. However on the flip side, since they are remaking base PSO2 visuals anyway, I wish they'd only go 100% and synchronize character models completely. Giving old players a few free fashion items and unlocks will be enough to bribe everyone to accept the new system.
Synchronizing 100% personality models does not seem simple. The dilemma is that the old outfits and layer use are modeled to fit the older pso2 body. To be able to synchronize it, they would have to recreate from scratch (haha pun) 8 years of makeup. That is unlikely to happen. Well, I mean that I would be ready to shed a certain proportion of these cosmetics to keep things intact across versions. As long as there's a continuous feed of cool new things to replace it, I do not mind. I constantly rotate out my older looks anyway. As long as the character versions translate 1:1 it'll still feel just like mine.
I'd envision a large complication to this involves a lot of the makeup from the Western side of things that were exclusive to collaborations, promotional events, and events which no longer exist. The instance I can think of is the Monster Hunter Frontier Z collaboration where I can envision the clothing and weapons could definitely be provided a visual upgrade together with everything else but that I do not exactly know how the licensing or how the lawful side of this cooperation works where I'd wish it was as simple as Sega going through and upgrading the assets but I don't know about just how much Capcom is involved in that process.
The same is applicable to collaborations like the Final Fantasy XIV cooperation 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 be able to upgrade assets . When it was purely just Phantasy Star-related things (such as character outfits, cameos from different games, or alternative Sega-related properties) I could envision that this probably would have been done, or would be done. But in the worldwide version we don't have the existence of Cougar NX so I do not know if there are other complications regarding Sega's own properties that might also contribute not to updating everything they could within reason.
I can envision that probably out there we'll still see somebody wearing those old collaboration items even if they aren't rigged up to the very same standards as fresh makeup in a similar manner and that there would have been outrage if it had been made unusable or obsolete. Collabs who have had their cosmetics removed nevertheless have their assets exist on the sport so those will probably still be accessible for jp players.
if you are interested, you can browse them in detail. URL: https://www.pso2ah.com/