I think given that BG3 needs to work seamlessly as a single and multiplayer game, and a multiplayer game that supports party members acting adversarially to each other, separate inventories are necessary.
No, they really aren't. It would be more than enough to have separate inventories "by player" rather than "by character". Which in practical terms would translate in an unified one when playing in single player.
Party control in Baldur's Gate 3 is a complete mess that begs to be addressed. SAY NO TO THE TOILET CHAIN
