There are a few reasons why I think this would be a good change for the future of PSO2. All opinions ahead.
Limited items people want may not be accessible to them. Not being able to log for extended periods of time or simply not having enough money for the battle pass. Many people would love to buy limited items off of player shops and since this is an MMO trading is a major part of the experience.
Collab gear can be traded so why not battle pass gear? If you're gonna let one why not the other? To me this makes little sense by restricting battle pass items to accounts, but not collab items.
If you won't allow trading them then why not exchanging them in for a currency? Let players get rid of these items they can't use in their inventory and trade them for things they can can use. This will save a lot of headache for players if you're sticking your feet in the ground on this topic.
What I posted cam be used as an argument for the Regol sets to.