Frankly it's just slightly worse than people buying a house, then going rogue and using it with their allies as a safe zone inside the homeenemy village. We've seen Freezehud do that with the house next to the Kage house, also was it Ryuusuken who owned the house next to the gate and was letting any non-leaf hide in it?
Kages definitely should be given an instant eviction command, as this feature is clearly abused in pvp.