Gosh, this seems so complex. On the one hand, kudos for maintaining the original game intact so there won't be a riot over changes people do not like. But on Phantasy Star Online 2 Meseta the flip side, since they are remaking base PSO2 visuals anyhow, I wish they'd only go 100% and synchronize personality models entirely. Giving old players some free style items and unlocks would be sufficient to bribe everyone to take the new system.
Synchronizing 100% character models does not seem easy. The problem is that the old outfits and layer wear are modeled to match the older pso2 body. That's not likely to occur. I mean that I would be willing to drop a certain proportion of those cosmetics to keep things intact around versions. Provided that there's a continuous feed of cool new stuff 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 will still feel like mine.
I'd envision a massive complication to this entails a lot of the cosmetics from the Japanese side of things which were exclusive to collaborations, promotional events, and events which no longer exist. The example I can think of is the Monster Hunter Frontier Z collaboration where I could envision the clothes and weapons could unquestionably be provided a visual update together with everything else but that I do not exactly understand how the licensing or how the legal side of this cooperation functions where I would wish it had been as easy as Sega going through and updating the assets but I do not know about how much of Capcom is involved in that process.
The same applies to collaborations such as the Final Fantasy XIV cooperation with Odin (which exists as far as I know) where I don't know how much of Square Enix is involved in that for Sega to be able to upgrade assets there. If it was purely just Phantasy Star-related items (like character outfits, cameos from different games, or other Sega-related properties) I could imagine this probably would have been done, or at least would be carried out. But in the worldwide version we already don't have the existence of Cougar NX so I don't know if there are other complications regarding Sega's properties which may also contribute not to upgrading everything they could within reason.
I can envision that likely out there we will still see someone wearing those old collaboration things even when they aren't awakened to the same criteria as new makeup in a similar manner and that there definitely would have been outrage when it had been made obsolete or unusable. Collabs who have had their makeup removed still have their resources exist on cheap meseta pso2 the sport so those will probably still be available for jp players.