I think the Borg shoulda been invincible from the beginning. Non of this non-threatening stuff, as soon as someone is seen by a drone it should scan them and determine if they are a useable resource regardless of how threatening they are. The Cubes should be able to just coast on through fleets dealing death and taking what they need without assimilating an entire planet unless they need the drones or some information. They shoulda been wholely about advancing their tech and appropriating their resources....and maybe wiping out a few highly advanced races to get their tech. They shoulda been like evil-Q's, only interested in improving and expanding.