Okay, I looked all over and from what I could see, there is no Aliens. I am talking about Aliens from Aliens 1 2 3, Resurrection, Aliens Vs Predator type Xenos. I think the general format should be something like this, of course if a modder decides to do this, I wouldn't care if you followed it or not since I would love it either way!

XENOS

Queen : Large Xeno, large damage protection from all things except fire. Able to lay a lair in which its bottom half turns into an egg making part, allowing new units to be created with different keys like (C) for Drone, (E) for Preatorian, (X) for Runners, etc.
Weapons: Claws, Tail, Ability to shoot eggs?, its weight should be able to trample human sized actors.

Drones: Durable, resistant to bullets and laser weaponry except fire. Average moving, able to climb walls and jump high.
Weapons : Claws, Tail, Ability to Spit Acid which damages enemies armor over time or kills them out right.

Runners: Quick moving, killing machines. Able to move quickly across the surface, scale walls, and leap forward very far.
Weapons: Claws, Tail, Pounce.

Praetorian: The defenders of the den, these Xenos are tougher then the standard alien strains as they are bred specfically for protecting the queen and the eggs. Very resiliant, durable, and deadly.
Weapons: Claws, Bite, Charge, able to use its arm as a shield and the ability to resist many weapons and attacks.

Facehugger: Small, agile none violent xenos, their sole purpose is to find a host, inject it with an embyro, then die.
Weapons: Facehug actors without helmets, once done, it dies and the actors later die spawning an alien.

Any other suggestions?

Very extremely hard, nigh on impossible to script even in Lua. Would be laggy as hell too.
This is unfortunately one idea that probably wont ever be given life.
Sorry.

Go into the modmaking forum and beg them to finish the pred mod cause thats probably the closest your ever getting to this without making it yourself

Technically, the growing process of aliens require host body to evolve from face-hugger to baby alien growing to final form,
that makes those creepy creatures to be even more disgusting and terrible (getting infected by aliens and die mutilated)

That evolutionary system is almost impossible in cortex system of combat, plus, current scenes are not very helpful.

I guess we could simply skip the "impregnation" step and make the queen spawn eggs, without face-hugger process...
If anyone could provide an efficient evolution script for the queen, which switches between different classes of eggs,
I would code and sprite them gladly (I already have two kinds of aliens fully functional).

Sounds like the pred mod is going nicely, are you planning to release it?

Nope, there's just a bunch of predators which is supposed to be the same in evolving phases,
5 hunting devices or so and a couple of prey aliens, nothing really important, but be very aware what
without scripter's help that mod is DEAD & BURIED before anything will be released.

Well, if only I'm not busy with college final project, I could help you a bit, at least on the upgrade system.

Anyway, here's an idea: just have them spawn from their egg as a chestburster. Then they could 'upgrade' themselves into the various tier I castes (worker, runner, warrior), which could upgrade themselves into tier II castes (praetorian).

Another idea would be the aliens still have facehuggers, but they're durable. And when they infect, they immediately burst into chestburster, which can quickly turn into warriors.

Facehugger = acrab with jump.

And to help them 'infect', have Drones able to spit 'webs' which stun the enemy.

This is kinda inspired by AvP: Extinction.

Help its always welcome but you seems to like not to read me, trooper
Facehuggers = a lot of scripting problems, growing up and evolving = more complex problems

Those ideas are great and sounds pretty fun, but without people willing to help, are useless
I'm definitely going to move on to more easy to understand engines like UDK, as a wise warrior said once:
I'm swinging my sword inside empty dungeons and I'm getting old.

Eh, for starters you could modify my Cordyc upgrade codes to be done by timer instead of button press etc.
Maybe tell me what kinds of functionality you want (upgrade-wise) and I'll tell you what possible codes you (or some other free scripters) can use.

For example...

Queen egg laying: Cordyc Mother Node script, modify so it pops out Egg actors with randomization. Have the egg actor a Lua script which times its age, and when a specific age is passed, have it 'swapped' with a Facehugger actor (or two).

Facehugger infection: Have facehuggers get a Lua script which detects if there's any nearby, non-allied actors, and if there are, instagib it, and spawn a chestburster (or just plain adult alien) in its place. Delete facehugger afterwards. Maybe add a bit of gold when you successfully facehug.

Alien growth: Have chestbursters or basic adult aliens the upgrade system from Cordyc. If there's enough gold (or killcount, or other variables), make it be able to transform at the push of a button. Apply modified script to Praetorians so they can upgrade into Queens when they've got enough (insert variable here).

Really, if you're creative enough, you could see different ways to code these beasts.

Yeah, really, the entire mod is pretty much made with the Cordyc. I don't understand why you seem to think you can't just edit it.

Miggles, I focused all my attention and modding hours to .inis and sprites, ignoring completely scripts,
that's why I'm unable to "create" lines of script from 0, allowing me to create "very nice" but not-functional mods.

The other reason is my priority are the Predators, aliens are just preys but they must be reliable to sci-fi culture.

Carriontrooper, I tested the cordycs... they look like they have everything needed for aliens except for some tweakings inside the scripts,
I promise to give a shot to it and I must say sorry because I have underestimated them, they're amazing and pandemic, very good job.