I have realized that in several mods - as will be in 1.2 - aliens regenerate slower, faster if there is creep around, even faster near Basilisk (healer) and booster. This is an excellent idea, and brings a hell lot more balance to the game, however, I have another suggestion to make:
Aliens can "eat" human corpses and get health from it.
Aside from the idea that someone could make a gore-mod (with human guts and limbs liying around and some blood + aliens turning into green slime one can slip on), this would make the game a hell lot more creepy and add some depth to it, for it would not be a good idea for humans just to run and let aliens feed on their dead buddies' flesh or maybe to very well do so to prevent them from having even more food.
I think it would be best to just have to slash at a human corpse to get, idk, the number of health points per slash you make when hitting human feet or something.