Is it possible to put a gate, door or transition into it, to stop goblin NPCs wandering in and becoming a hazard for missed attacks, cleaves etc hostiling the Squat?
I don't believe there's a gate for that placeable, but it's not a huge issue. Cleaves won't hit non-hostile units, and to attack one you'd need to right click it and specifically select attack.
Just ignore them, yo!
The only time I could see it being a real issue, is if you're having a Mage-battle with AOE spells, or you're loose with a special attack like KD, or Disarm.
And area spells.
I fireball all over that hizzzouse. This suggestion has merit.