I agree. Instead of having the retainers each have different inventories, let them both show you the same combined view. In fact, let each retainer put up 40 items, for a total of 40. in other words for everything except the gear and venture menus, they should both do the same menus.

Separating them like they are now serves no real gameplay purpose. i suspect it's more a technical/db issue, but it's incredibly cumbersome and poorly thought out as is.