Am not sure if this is the right place to put ideas for game play...but I couldn't really find anywhere else. After playing in some open instance teams, there were some ideas that sprung to mind.
1) Having some sort of signal flare for people to find you on the map. Was on the Big Dig the other night and spent more time looking for people to join the team than actually go about completing the mission. As you only see people when they are within a certain distance, maybe have an option on the team bar at the side to have a flare flash up on the screen, or on the mini map to give people an indication of where you are.
2) Nothing major, but I thought of a little something to make the open instance teams more cannon. Have the highest ranking player be made leader of the team. Not sure if this should be made the case right away, when someone joins the team or if the leader had to leave.