I guess the big thing about this whole thing is .... the difference between real life and only one life to live verses the reality gaming world where you have an infinite number of lives no matter how many times you die.
That's why, when you say, "Players should be paranoid when isolated so that they choose to fall back rather than fight-to-the-death. Countless are the real-life scenarios where skirmishers occupying buildings would run or surrender rather than put up a fight to enemy closing in.", the first paragraph applies, there is no paranoia. UNLESS it is induced by game mechanics ... i.e. a player who finds himself isolated should be denied access to player controls and the AI forces him to run like a scared rabbit. There is no threat of mortality, like there is in real life.
Really not sure how to over come that lack.