This was something I suggested back when ADH was still around.
As you know, the current friends list is pretty simple, it just shows if a given friend is logged into the game and if they are in a match.
I would like to be able to see what kind of match the friend is in. Many times I will see a friend in a match and while I would like to fight with (or against!) them, often they are in a match type that I don't want to play at that time (or care for in general).
Being able to see what match type they are in before joining (and possibility throwing off the match balance) would be a very good addition IMO.