Gosh, this looks so complicated. On the one hand, kudos for meseta pso2 keeping the game intact so there won't be a riot over changes people do not like. However on the other hand, since they're remaking base PSO2 visuals anyhow, 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 take the new system.
Synchronizing 100% character models does not seem easy. The dilemma is that the old outfits and coating use are modeled to fit the older pso2 body. In order to synchronize it, they'd have to recreate from scratch (haha pun) 8 years of cosmetics. That is not likely to happen. I mean that I'd be ready to shed a certain proportion of those cosmetics to keep things intact across variations. As long as there's a continuous feed of cool new stuff to replace it, I do not mind. I constantly rotate out my old looks anyhow. As long as the character models translate 1:1 it will still feel just like mine.
I would envision a massive complication to that entails a great deal of the cosmetics from the Western side of things which were exclusive to collaborations, promotional events, and events which no longer exist. The instance I can think of is that the Dragon Hunter Frontier Z collaboration where I can envision the clothes and weapons could definitely be given a visual upgrade together with everything else but that I don't exactly understand how the licensing or how the lawful 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 how much of Capcom is involved in that procedure.
The same applies to collaborations like the Final Fantasy XIV cooperation with Odin (which exists as far as I know) where I do not understand how much of Square Enix is involved in that for Sega to have the ability to update assets there. When it was only just Phantasy Star-related items (like character outfits, cameos from different games, or alternative Sega-related properties) I could imagine that this likely would have been achieved, or would be carried out. But from the Global version we already don't have the existence of Cougar NX so I don't exactly know if there are other complications seeing Sega's properties which may also contribute to not updating everything they could within reason.
I can envision that probably out there we'll still see somebody wearing those older collaboration items even if they aren't rigged up to buy Phantasy Star Online 2 Meseta the very same standards as fresh cosmetics in a similar way and that there would have been outrage if it had been made unusable or obsolete. Collabs who have had their makeup removed still have their assets exist on the sport so those will likely still be available for jp players.