I just had a eureka moment.  So crossing sucks especially when you shoot someone accidentally and loose your exp.  It happens to me like every fifth game.  Now the problem with the current system of saying x when you cross is no one pays attention to them.  I have never held my fire because someone said x. Its because people say it all the time and your too focused.  Also, saying x means you don't know who is crossing who or when it is clear.  This is where it dawned on me.  We need an 0.

So its really simple!  You say x when your crossing....and o when your clear.  Put it to team chat to narrow things down.  So that way when you see an x you know not to fire if your in a crowded area, and when they say o or 0 you can open up.  Saying x just doesn't give enough information. We need to say o when crossing is complete. 

The more people start using it in game the quicker it will catch on, just like saying x did.