Making a game realistic isn't hard. Making it realistic and fun is. Want ultimate realism? Once you die, your game locks you out permanently because, guess what, in real life once you're dead it's over. End of story. Sound fun?
Reminds me of some games in Operation flashpoint(the original one) and Arma where respawning was disabled.
If you were unlucky and died early, you might be stuck a full hour flying seagulls while the remaining team tries to take the objective. It does something with your motivation to stay alive, and you will be hugging cover more than you are shooting.