I like the Kafer too, because they really are so...alien. And we're basically their worst nightmare, so their hate for humanity is justified. I wouldn't second guess them at all. GDW really did a good job on them.
If the players really try to dig into how they got here, I'll probably say it's some sort of AD2300-level drive. I'm trying to stick to as much canon as possible, but I'm breaking some of it obviously. I do intend to have the Ylii too, at protected Kafer ground bases and such, so they don't get discovered until later. I can use the excuse 'The Ylii did it."
A wormhole would be neat, because there'd be no way to 'plug it'. Humanity would have to start reverse-engineering Kafer/Ylii stuff, and head in themselves.
Then there's a totally new campaign
I'm also giving the Kafer some goodies from the Darktek manual. Giving the players the options to use the stuff to is an added bonus I'd love to see, especially the 'feed' problem.
EDIT: I just can't wait for the first combat encounter with them, while they're still 'stupid'. Man oh man, those players are gonna get it handed too 'em.
