I guess you don't like surprises in game when you die to an unknown enemy randomly. That's ok, though there is some fun in that imo.
New non-armored regular enemy. 75 hp, 0 armor, has melee acid attack which ignores half of target's armor, unless it's structure. Now they are in place of some portion of zombie hordes and are about as rare as reapers so they affect weapon setups a lot, both in roaming and during escapes.
New rare armored enemy, immune to fire. 150 hp, high armor. A predator who can jump on/off cliffs, regenerate off combat, leap on top of players and stun them for a short time, and overall is really fast, dangerous and unpredictable unit if you don't have counters ready. This gets boosted to extreme when generator is down: prowler can kill the entire team if players don't stay together and have a bunch of AP on their weapons. Also, flares scare prowlers away.
New rare enemy. 100 hp unit with ability to charm players. Often you can't possibly see her before you get seduced, so you must listen to the sounds she makes which can be heard at a big range. If you get caught you start to walk towards her very slowly, and other enemies ignore you during that like with larva. If no one kills seducer or use communicate ability on you in time, she will rip you to pieces with claws (admittedly, they aren't very strong, especially against heavy armor).