Wow, sounds like fun. My first comment is that, if you give them really souped-up characters for this one-shot, then guide them through standard character creation, you might need to manage their expetations more than you normally would.
Also, for their first run, you're sending them to space? That'll probably make things more complicated, especially if they're never going back to space.
If you're giving them pre-made characters, how about turning the perspective around? The PCs become a bunch of workers in the secret S-K facility, with their issued equipment and authority over the other workers, and have to fend off a shadowrun of uncoordinated runners you've also made up? That'll show them what not to do, what they might expect, and afterwards, they get to make up their own characters, and hear about a Thor Shot made at South Africa later. (Maybe those runners sent in as a distraction, or by a third party with know knowledge of what the Ghosts are doing?)
