Cept I highly doubt any space faring planet would be taken over easily. Every planet that has space fairing tech, is under the Republic or the Empire. Since this scenario counts both sides working together, they entire galaxy is united under them. That means any tech is going to be apart of some organization that would be raising flags as soon as the flood got onto the planet. The flood may take the planet, but they would never be able to leave the planet. The blockades would stop that. Plus Hyperspace would not work as any blockade fleet is bond to have a few hyperspace jammers.