Hm, I kinda like that idea... There could be a couple problems programming it, since right now the 'radar' just displays things within a certain range and inside the 'vis' of the player. I think Timbo could handle getting around that though. >.>
If you want to see the progress until reaching next stage, just look at the scoreboard (usually tab) the top part will say what stage you are in, and how many kills are left until the next stage.