The new radar is excellent imo. The biggest improvment over the old radar is that you can now exactly see what hallway your teammates are in, instead of kind of guessing "oh, they might be in B-tunnels, maybe." It helps in knowing that they are watching your back, especially when you can see where their gun is pointing.
I like the idea of enemies showing up when your teammate sees them for a period of time, but I think requiring a radio "enemy spotted call" to show up on the radar would be more realistic. Seeing dead bodies permanently on the radar would also be helpful.
I haven't played around with zooming in or out, but obviously showing the whole map would be the best way to go, if possible.