Thanks for the interest so far. If it makes it any easier, I wasn't thinking of a building/vehicle that could be entered by the player, just a means of holding guard troops instead of having them standing around or having to teleport them in.
The vehicle basis would mean that waypoints could still be added for the cargo groups and the occupied barracks would be targeted - I thought armour class might be good so that it would be RPG'd etc but with enough armour to take several hits before being completely destroyed (by which time surviving cargo would have ejected)
I have a bit of a grasp of the config issues, but I'm pretty ignorant on the modelling side - all I can guess is that the barracks would need a door defined as the 'eject' point and maybe a crew so it 'reacts' to attack. I don't think it would need to be 'sided' as that would be determined by its occupants.