After playing NS for well over three years and into its fourth their are somethings that an opportunity like this can yeild.
Add a fifth upgrade for aliens -
Gorges: Ah, babblers... they were the best defencive attack upgrade the aleins had. Sad to see them go into the trash but perhaps they can be pulled out and a cap placed as to the number a gorge could spawn. I'm thinking one per hive activated with two or more hives.
Skulks: 'Displace', a new upgrade that would be active with one hive. Would operate like charge does, draining the adreneline bar till it emptied. Either creating a false image (mirror images) or distorted images of skulk(s). Many players choose something other than adrenaline with one hive and MC as first chamber. This would encourage adrenaline as an upgrade.
Lerks: Easy, bring back the spike! Activated with a second hive. I believe is the ultimate ranged attack for the aliens. Of course add a falloff (perhaps based upon adrenaline) and a slight spray to the ability.
Fades: Perhaps one of the most complete lifeforms, but still lacks a true 3rd hive attack. Acid rocket is very useful from range but not in melee. Perhaps a poisonous bite? (ideas needed)
Onos (Oni): Countless times I've scene a lone Onos run into a pack of HA/HMGs with only one hive, one upgrade. Such a life form ment to be the pinicle of Kharaa needs a good one hive ability capable of defending the last hive. Perhaps a 'Frenzy' state that would restore a % of HP based upon damage inflicted to the marines. This ability would drain the adrenaline bar much like charge. Another optin would be to bring back the paralyze stingers, stomp is a wide range ability with a short effect, while paralyze was a focused attack with a longer effect.
Chambers: Why not make the chambers more vien/infestation styled. Instead of having a OC chamber stand out of the ground with no infestation nearby perhaps have it creep along the walls and celings. Using a sack like structure filled with explosive fluid that would project a cone of spikes to the nearest source of nano tech (aka marines). The sacks would be very similiar to the egg and could regrow too. Perhaps even allowing the infestation to feed the chamber (aka gorge spending more res) to add more explosive sacks to the OC.
DC, MC, SC could function as is just instead of an explosive sack their would be carapace armor slates, little blue sensory tenticles, or the horns (black things on the MC).
Another chamber could be added too. A sack filled with umbra gas and | or the spoar gas. Both would also be very effective against jetpack marines or deflecting bullets from distant marines shooting down a hive. If a marine shot an OC the bullets would cause the sack to explode sending a hail storm of spikes back. GLs, the potential flame thrower, and hand grenades would become very useful to take out such structures.
The chambers would not form obstacles for high life forms, nor block halls with walls of lame / whoa.
Weapons: Flame throwers, hand grenade refills at armories, and a (remote/time delay) bomb device would be very useful.
Structures: An idea to add atmosphere to the game would be to limit the commander's view range based upon where marines are and concentrations of infestation. As infestation naturally feeds off the nano particles a commander uses to see the entire map with. A shroud or brown out where a least amount of nano particles would be only makes sence. To counter this shroud and help out squads of marines, thier could be an upgrade that would give marines a pair of 'nano sticks'. Their function would be very similiar to that of a ping and would allow a window into the portal of infestation for the commander and squad. For outdoor maps this feature could explain how a commander is able to generate nano particles and structures from air. Overtime the nanosticks would fade and get overtaken by the infestation. If the source of the infestation is eliminated than the nanostick would continue to glow and emite nano particles.