Having been in a large battle recently, the thing that worried me most was our own guys killing each other. In the heat of battle, it is really difficult to tell friend from foe, and trying to use mouseover to identify each person is just too time consuming.
What I propose is an option to create a green outline around people in the same group as yourself. This would be similar to the outlines used to see behind stuff, but green. The button to toggle this could be next to the buttons that toggle claim and village sight.
Since I am talking about team UI, I would like to mention that having portraits of the people in my group are not particularly helpful. Having the memorized name of the person would be more useful. Same for combat with people.
It would also be helpful if the flower menu that appears when clicking on the team portrait were to appear more toward the center of the screen. As it is, the buttons are often unreadable and/or unclickable.
To the moderators: I think this idea is important, so please feel free to banish any off topic crap.