There is a #secondshape (or something) command. So... you could, for example, have a unit turn into a custom monster on death, that has 1 hp, 0 for all stats except attack, 200 encumbrance and -10 reinvigoration, and an AOE 9 fire attack. And the unit icon could look like an explosion. How's that?
Edit: Also, combat only lasts 50 turns (or was it 40?). Either way, you can set reinvigoration up to -7 without risk.