Friendly fire - isn't. Things that must be together to work usually can't be shipped together. Radios will fail as soon as you need fire support desperately. Anything you do can get you shot - including doing nothing. Make it too tough for the enemy to get in, and you can't get out.
Tracers work BOTH ways.
The only thing more accurate than incoming enemy fire is incoming friendly fire. If you take more than your fair share of objectives, you will have more than your fair share to take. When both sides are convinced they are about to lose, they're both right. Professional soldiers are predictable, but the world is full of amateurs. Murphy was a grunt.