This is an idea I've been kicking around in my latest pnp creation that I thought might be applicable here.
What if you place the risk of perma-death entirely on the players side. What I mean by that is the player gets to choose when he or she wants to put it on the table.
The way I would envision this system working is, when a character goes down, he or she is badly wounded, and out until one of the characters who survived the fight is able to revive him or her, however the player may force the fallen character to get up again, fighting until they can go no longer, if they take a certain amount of damage while forced to go on, they die permanently.
This would allow the player to keep going despite early setbacks and in challenging circumstances risk his characters lives to win an encounter. However it also mean characters don't die, unless the player is willing to risk their lives for the result her or she wishes to achieve.