SpawnEntityOnDeath definitely doesn't work, so I think @wowgetoffyourcellphone did something different or it was broken without being all to obvious back then. If you want to add a unit as if trained for example, so that the simulation knows of it, and place it where the old one died instead. An example is QuickSpan in binaries/data/mods/public/maps/scenarios/pickup_test_map_triggers.js.