Homeworld ships a are awesome but it Homeworld itself that rules, without Homeworld style combat, you will find your ships to be little satisfaction. People tend to make mods for universes/fiction which don't have games of the same genre or (decent)games to speak of. Homeworld is neither (though it isn't strictly 4x) and is superior in terms of combat depth so there is little reason to make a mod. Not to discourage you though, it is possible, but not how you're suggesting(with the poly files, different engines screw it up).