But...why not just mount weapons on the space station? You can get a lot more guns built into the station than can be carried on the mobile structure.
Mobile Structures as giant Omni-pods? If expecting Dropships, you can rapid-transfer a Rattler & friends to the combat space station. If expecting a swarm of ASF and you don't have an ASF swarm of your own, another Mobile Structure designed for shooting down ASF. If the opponent likes to use missiles, you tag out for a MS designed for anti-missile setup.
You would also be able to bypass Fire Control limits this way as the Mobile Structure's weapons would not be part of the Space Station's weapons array.
Of course, you'd need a nearby completely innocent cargo space station to store the various Mobile Structures, which means you need to get the relative tonnages of a Mobile Structure to determine how many can fit into the cargo space station's bays.
This also runs into fun numbers of how many tons of weapons you get per 1000 tons of Mobile Structure, vs tons of weapons per 1000 tons of Space Station.