This sounds like it could be a great way to set up friendly competition, but it is very susceptible to both exploiting and stirring a more negative/hostile community, in my opinion at least.

I think a "rival" system that you find in some other games would be more fitting, it would pretty much be a friends list but for opposing factions. Say you you have a heated sniper battle with some one, or you repeatedly butt heads with some one when sieging a base, you would go "Grah, you're a great warrior, we should do this again sometime!" and add them to your rival list. Y'know just like in the TV shows.

Or it doesn't even have to be mutual, if you add some one to your rivals list it could show a little marker over his head whenever you bump into them on the battlefield again (could also lead to exploits, not a game designer).