In 2008-9, there was a brief attempt to create regional Seneschals, but the role wasn't defined or well-supported; they had no mandate or definition in Kingdom Law; and little or no understanding from the populace or group Seneschals. So they did not prosper.
Given the ever-increasing demands of the Kingdom Seneschal’s role, it may be worth taking another look at that and try to do it better. But that doesn’t offer New Zealand the multiple benefits of a full Principality, the utility of broad national support provided by local Principality Officers, nor any of the in-game benefits of having a Coronet.