i think wat he was trying to get at is like have the option as a human, u customise ur self a bit, u kno different face, different outfit ( same colour code) and maybe a bush hat or a bandana?
as for aliens..... well.. take the zebra for an example, each one has its own different stripes... but can we tell them apart? hell no. but if they were differnet so we could, then how would we kno that it wasnt a horse or big donkey?
but i spose that if they improved the ingame blood so that every kill u made u were splashed with blood? and u get a clean alien if u die? then your could tell the pro's from the... well not so pro's.