Atlantis probably has some manufacturing and buisiness districts, but it's no weapons plant. Either way, it's obviously not making an appearance here, as you all know perfectly well.

~o~0~o~

+[i]WrongEndofTheRainbow[/i]: 
I'm highly amused by the idea of a building suddenly appearing in high Tatooine orbit. But there are some unaddressed issues that I noticed.
1) The Citadel isn't airtight. Not to say that parts of it wouldn't be, but on the whole, it's made for atmospheric transfer and entry - even if you're dropping it from an transuniversal portal. You'd have quite a job of sealing it up, and would likely lose a lot of atmosphere. Force fields wouldn't be much help, either, because they seem to be configured to only prevent organic matter from passing through. Even if you did reconfigure them, they [i]still[/i] wouldn't cover the whole building, or even most of it.
2) You've got a substantially larger amount of forces than pretty much anyone else here. Then again, with the likely atmospheric leak, that might be reduced.
3) I don't quite see the Combine playing nice with anybody. Sure, your Citadel's "crew" might play nice (because they're essentially stranded anyway), but as soon as contact is made again, then there's just going to be an invasion. Maybe I'm wrong, but what else do the Combine [i]do[/i]?
4) People have already pointed out the multiversal empire vs. multiversal empire thing. That can be sorted out with some talking about respective back stories, though.
5) This is actually an argument in your favor - despite the larger amount of forces, despite the multiverse problem and the Combine [i]will[/i] invade problem, I'm almost tempted to allow you in. You can't make more Stalkers (no Nova Prospekt) or any other human-cyborg-Combine-things, you've got no thrusters, and you won't have much atmosphere or CO2 scrubbers or O2 tanks or astrogational sensors.

Overall, I like the idea. But you need to address those issues before you can play it.

+[i]Click This[/i]: 
[quote=Sep]
If you ask nicely Raidne might let you keep some that were already in launch tubes :P
[/quote]

^That'll work. The rest were lost in some quantum disentanglement technobabble, or were ejected out the hull in a breach, or are too dangerous to actually keep around because they're spewing gamma radiation everywhere, or are completely useless due to misaligned zero-point targetting gyroscopic technobabble, or something.