Also, it is completely unrealistic that I shouldn't be able to evolve(if I had the ability to) in the presence of the enemy. Plants don't stop photosynthesis in the presence of grazing animals.
Hmm, yes, tremulous is realistic! Aliens are realistic! Biomass can reform and even gain mass in less that nanosecond without taking it from surroundings(evolving)! Sorry, but that argument fails automaticly : P
And about that human role changing....the teams are completely different, why should they have the same abilities? For example, should humans be then able to buy weapons everywhere too? Humans can only change their role when there is an armory near you, aliens have only one place where they can't do it, right infront of the enemy. Unbalanced? I don't know, but your reasoning fails.
(my opinion is that things are fine as they are now, I really can't back it up with arguments, you would have to use shit load of reference to make a point that would please even most of the people)