Mostly they don't bother with primitives, as there wouldn't be anything "new" to acquire. Unless they're short on drones. I believe the best and most reliable drone is one that is "home grown" in a Borg hatchery. Because there's no chance of it defecting after unexpected separation. No prior life memories to be lingering about in the mind.
But as depicted in TOS, the Organians are seriously powerful... considering that they immobilized the Klingon and Federation star fleets everywhere. If it was only within a sector or group of sectors, then it would be a different story. But as written, their powers can stretch across a galaxy. That's HUGE. Imagine the power. No Borg could stand up to that. This is why, as written, they'd make an amazing fail-safe for the Federation.
Not that this would be easy to leverage while maintaining a good story. "Best of Both Worlds" was highly flawed, when considering how the Borg were utilized as an enemy in future series and movies. Because ONE Borg cube wiped out over 40 starships... and later on in other engagements, one Borg cube wasn't shown to be that powerful. I think the Borg would have waited for more cubes to appear before attacking Wolf 359, to ensure complete destruction of the Federation and its allies. Anyway, presuming the "sleep" command wouldn't work again, let's say the Borg returned with an armada. How could the Federation possibly survive this? Run to the Organians!
To keep that from being a permanent failsafe, what the Organians would do is immobilize the Borg armada... but then the Organians realize what this means -- the Borg collective will be aware of Organia and the powerful entities there, and would never leave them alone. What they then do is broadcast a message to all Borg, to leave the Alpha quadrant and never return or else face destruction. The Organians would then tell the Federation something along the lines of this:
"We have stopped your war and warned the Borg to never return. But that is no guarantee. Now that they know who we are, they will undoubtedly remain curious. We remained here in peace for thousands of your Earth years, but now the indigenous forms of life in this sector have advanced enough to become bothersome to us. We wish you no ill will, but we cannot tolerate these incursions to our planet. We have already made plans for a suitable relocation, despite Organia having been an ideal place for us. We regret having to do this, but we are leaving and you will not be able to follow. The Treaty of Organia is over. You will have to sort out your differences with other beings on your own terms. We wish you well. Good bye."
