It would be great since you are redesigning the diplomacy screen to include some additional indicators.
One that I really feel is missing is "active" trade agreement, not a trade route, but trade agreement. Otherwise you need to open up communication with the faction and see if the "Let's see if we can come to a trade agreement" is greyed out or not, too many $#*^& clicks....
Was addressing this.
As for the rest, I wholeheartedly agree with the desirability of being able to see how much time you have left on your trade agreements.
I would also like to see how the AIs feel about one another easily. The info is there (somewhat), but is buried.