I like the basic idea of it, but I don't like the way the level ups are made. I feel like the levels should just be the distance you can see the auras (if a player is too far from you at lvl 1, their aura wouldn't show) and have it default to show red/blue auras. I also think it should show an aura for allies/enemies hiding, which could be built into the leveling (level 2 you could see the proper ally/enemy color for henges, lvl 3 would be able to see auras even when ally/enemy is hidden).
[EDIT:]
Although, I don't really think the blindspot cone is necessary, it would be really hard for enemies to even try to take advantage of it.