I'm making an attempt at subverting one of the AI race planets and I've setup shop with several influencer starbases around the target planet. I'd like to upgrade the starbase to the next level, but when I use a constructor to do so, I am only presented with the options of adding weaponry or the diplomatic branch upgrade. I would like to go the influence upgrade path, but for some reason it's not showing up even though I have recently completed researching Advanced Trade. Are there other technology requirments beyond Advanced Trade that I am missing somewhere in order to upgrade via the influence branch?