tactical play

I wish that every time a player is killed in the game there is a deduction of the points (score), so players have to play more the tactical way instead of run and gun.

I'm not so sure about this, each team should have a mix of high and low risk players and tasks, each judged and given points based on objective and progression achieved in the game, then kill score added on as a bit of a score tweak. As far as I am aware the game seems to do this ok.

All deducting score will do is make people rage when others don't care or don't know. Perhaps this is an idea for a custom game mode or hardcore mode later on?

I agree with trying to encourage players to work as a team but I don't know about penalties. ....perhaps more incentives?