The import option is basically the same one that Freespace 2 mods have access to for use in things like the Freespace 1 port. There was no point in disabling this for Diaspora. But if you try to use it, it won't find any of the Freespace 1 ships and will almost certainly crash out or simply convert them all into Viper MK VIIs.
Now if you want to create a Freespace / BSG crossover, that is possible but I warn that it's not as simple as just importing the missions. You'd have to do quite a bit of table modding to make it work.