I agree - rerolling the dice is a complete no-go. We have our own way of saving party members (NOT the entire party, though), by giving each player a few (three) "wyrd points" to start with. Such a point can be used, AFTER a battle, or other tactical situation is completely determined, to alter a crit result of "irrevocably dead" to unconcious for a long time. This was particularly useful in our last campaign, where there was practically no magic, and lifegiving was absolutely out of the question. A character was absolutely dead if he had no wyrd-points left, or if none of the others could get to him and get him away (we had to leave one guy behind at at time, and flee the battle). Also, in some situations it was made clear that wyrd-points would NOT be allowed, where players had to make difficult decitions or perhaps were trying very dangerous, dare-devil actions ("Do you REALLY want to fight that dragon? OK, but this is a no wyrd situation"). Even in a campaign with magic, we tend to play low-level campaigns, and thus the wyrd-points are still neat (the "oops, you fumbled and killed yourself" just destroys the game - just putting the poor character out of action for the remainder of the battle can be better). But death HAS to be an option, to keep the fun and excitement. So if there are no wyrd points left, you DO get a chance to trip in the stairs, fall down and crush your scull. The players are still careful, and no one ever wishes to have to use a wyrd point.
As for rules and house rules, we do it slightly differently. We make a hasty ruling then and there (quick GM call), and then we discuss the rule by mail before the next session, in order not to lose game time. We try to keep the rules discussions to a minimum during play.
Oh, and we ALWAYS roll the +0 attack (although in the past, we played it differently). In a "must parry" or "stun" situation, we have ruled that it cannot cause damage; it's a pure "fumble check" (I'll have to re-think this one, though - perhaps open-ended rolls should be allowed to cause damage after all?...). Otherwise, it might cause damage, like any other attack.