I was reading the squad discussion, when I thought of a simple yet useful addition: the players should be able to mark a spot on the map without using coloured blocks. Now, you might say it would leave the map cluttered with useless markers - you'd probably be right, but I'm not talking about permanent markers.
Basically, I think that something like the flare from Age of Empires: it would create an icon on the map on the player's location that would be visible to player's team and disappear in a few seconds. Secondly, to prevent abuse, it would have a cooldown and/or be unavailable if more than X flares are placed by the team.
I don't think it's a necessary addition, but it may be useful while not very resource-intensive. What do you think of it?