Heh, by Spaceworthy it just means they can survive in space. Maneuvering in space is another problem entirely.

As for making the Citadel a spaceship by it's own right, I'll probably get my hands on some of the engine and FTL designs and use the Citadel's war factories to pump them out in small pieces, then have Stalkers and Transhuman maintenance crews assemble and attach them in various areas. The FTL would probably share the core area, or otherwise be near the core. It'd be a really ghetto spaceship, but it'd work. As for hoppers, yeah, most of the forces are made for ground combat. The mines would have to be attached to a solid surface.

EDIT: I'll be going to sleep now. Let's see what the GM has to say about my app when I get back.