I agree with this. when in camp, the player should have access to all party members and their inventories, regardless of if they are 'current' party members or not. I shouldn't have to remove a party member, add another one, and then do whatever I need, only to have to do that again to get back into the game. just let the player access everyone while in camp. This goes for leveling up as well.
The option to mass level up would be great, but maybe as an option to toggle on and off? I know some people prefer to only play with their chosen party members throughout the campaign and probably wouldn't want to spend time leveling characters they don't use.