Another popular house rule concept:
Medic: Leave models that miss their Armor save face down on the table. If a medic can reach them, roll to see if they can re-enter the fight: 1-2 re-enter with no penalty, 3-4 can't move but may still fire, 5-6 remove as casualty. You can add rules for helping wounded comrades move, morale effects, etc, until you're playing Stargrunt II

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(Why this is relevant to the thread: models that are hit by Kill damage dice don't even make an Armor roll, and are just removed as casualties 100% of the time. So the difference between a Target and a Kill is that one can be saved by the medics.)