I recently heard about the 3rd person view and that aiming with the mouse would possibly be added; i'm assuming this is all done through the map editor and is start till finish? will it be possible to switch between the bird's eye view/3rd person during gameplay and is 3rd person available during normal "star-craft 2" multi-player for regular units?
there was a minigame made through the map editor with 3rd person view, other then that i have no idea of what you might be talking about,
You can do this already with the warcraft editor, it's just a little unresponsive. But yea, a 3rd person / birds eye view toggle should be more than possible in a UMS map. Because its script-based though, it wont be possible in real melee/unedited maps.