This is a really simple idea, which I believe has been briefly mentioned before. I want to elaborate on it some more though becuase it encourages teams to fight together because as they die, their corpse will cause some sort of ability to activate. It will be a commander researched upgrade for each individual life form which gives them a passive on death ability. Once researched the life form will have this ability, and a small notification will be on their hud that it is activated.
Skulks (Xeno): On death, the skulk corpse begins a rapid enzyme reaction sending bacteria into a feeding frenzy. This causes the corpse to begin to bloat, until finally, it explodes, sending super dense bone fragments in all directions wounding any enemy within close proximity. It would have a short delay just like the original one.
Gorge (Rupture): On death, the gorge, now unable to control the bacteriums growth, begins to grow a minicyst in his belly until it blows through sending bacterium everywhere and creating a minicyst and small infestation patch where he dies. On hitting alien life forms it causes a small heal. On the marines, it eats away a small amount of their armor. This will be rather quick. (I believe this one was already mentioned by the devs, and I know by other forum members)
Lerk (Spew): On death, what spores the lerk has left in his glands are quickly expelled out filling a small area and causing damage over time like normal spores. Lasts for 3 to 5 seconds depending on balance needs.
Fade (Quicken): On death, the fade begins to slowly release the same bacterium that allows him to shift giving all units within range one quick shift in whatever direction they want by double tapping the direction key. Lasts for 8 - 10 seconds but only allows one shift per alien per fade death, so use it wisely.
Onos (Calcify): On death, the onos flesh begins a reaction in which it calcifies into a bone like substance. This allows aliens to use its body as a temporary shield while blocking marines from forward movement.
We want to encourage aliens to fight and die together. By giving them an on death ability, it provides support for fellow teammates who are in the area encouraging team play while adding more depth to the game in a very simple and intuitive manner.