Heres my thought: We write the storyline and the scripts and make it like a choose your own adventure. Certain actions provoke a different plot line. Some may be inconsequential and merge at the end, but others may result in catastrophic changes e.g. Khaak taking over the whole x-universe making life quite hazardous for everyone. Sounds good? If it does, help contribute by creating a thread with numbers denoting where in the plot it is supposed to go. e.g. you want to work on the opening sequence then it would be [plot name]-1. Easy. If you want to work on the next sequence, then move to 2, 3, 4 etc until we get at a point where there are two options. Once that happens, then there are two subsequent threads that can emerge. Call them, for example [Plot name]-4-1 and [Plot name]-4-2 respectively. That way lots of people can take responsibility for various parts of the story without getting all confused. We can link them in this thread, or a separate thread to avoid confusion.
Everyone got it? Ok heres my plot Idea.
Maybe we can work on the Khaak. Its pretty much assumed that they are an insect species, but there are so many other options to explore. I reckon that we can tweak this concept a little. lets presume there were a race of people who live in symbiosis. One host organism with a conscious bacterial colony style symbiote. Once they were attacked by some race in the deep dark past, the symbiote mutated to help the host combat their enemies. The hosts are eventually wiped out, but not before a symbiote manages to infect one of the enemies and spreads, eventually taking over the entire civilisation.
Several millenia later (and presumably several host species too!) this contagion is generally referred to as the khaak. Half of the challenge here will be to gradually build this picture. Naturally the story starts with everyone ignorant on how the khaak came to being, or even that there is a risk when coming into contact with these creatures. Back story? Maybe someone can work on how the purple triangles (maybe the ships turn purple once the host species is infected) came into contact with our infected friends. I would love it if we can make a race of pre-khaak bugs who are uninfected and appear neutral, even if they will attack on the slightest provocation. I imagine that if you open the comms to these guys you will hear crickets chirping!
Next step is the Paranid. They are the first to come in contact and unbeknownst to the rest of the universe managed to capture a few live khaak. Not knowing that the khaak are actually intelligent bacteria that infect an unfortunate host, they don't take many precautions against this mode of attack. The Paranid therefore start having problems, starting from where they are holding their prisoners and radiating outwards. This means that you go into Paranid space and some sectors have ships which are notably different (presumably they are purple with all sorts of things hanging off them. As they attack you the infected paranid pilots are shouting "help me!!" through the comms).
Next step is the Argon connection. Julian's dad has been captured so I presume he would be the first to go. Being not as threatening as the Paranid, the contagion would not be as active. Kyle went back to Earth, however and possibly the Terran xenophobia may provoke the infection to spread. We therefore have a seperate line of infection from that point.
From here we have the option of spreading the contagion to the other races. I would love it if the sum total of our choices affected the rate of spread and I would love it if various other choices could affect race relations e.g. Paranid at war with everyone, Paranid at peace with everyone, etc...
There definately should be goodies at the end of various plots. I thought if you successfully managed a peaceful interaction with the pre-khaak bugs, for example, you got a ship like an energy drone m6. The concept is that its main weapon fires drones that are entirely composed of energy so they are extremely short lived (a minute or so), have a weapon that they fire and have tiny collision spheres so they collide easily, and a reasonable amount of damage results.
I would love any ideas you have and would enjoy it even more if people got cracking on the plot. It may all be pie in the sky and the thread may sink. I hope not. I would love to see a final game result from this.