I was thinking about this a bit more last night.
I think the folder option is the best way to implement the feature. Basically, it would just be applied as an auto-filter to items you deposit into your bank and separate them in your bank into different categories that can be expanded/collapsed. This could include the following categories:
- Favorites
- Hunter Weapons
- Ranger Weapons
- Force Weapons
- Armors
- Units
- Shields
- Mags
- Consumables
- Disks
- Others
If this alone were implemented, it'd be a major relief for a lot of people (like me) who get lost in their bank easily.
Don't get me wrong, though. I think a Favorites feature would still help a lot, but I think it should serve a different purpose other than 'just' for bank sorting. My thought behind it is that items you favorite would also behave differently in some other menus:
a) A star icon will appear next to favorited items in your Item List.
b) They would be locked from being sold/registered in Shop Menus or Point Register so people could breathe easier.
c) Favorited items that are deposited would appear in the 'Favorites' folder in the bank, allowing for easier access to weapons that might be used in only certain conditions (like myself as I ALWAYS forget to bring a Cannon Rouge for boss rush quests).
PSO2 has all of this as a QoL feature, so maybe use that as a blueprint?