Leinad's idea isn't too bad. What if we make the North a Parliamentary Republic?
The Governor, or some other title, would be popularly elected but hold very little power, mostly a ceremonial position - like the President of Germany. The legislature could be a little larger and elect a Prime Minister or a Chancellor to serve as the head of government.
Depending on the size of the legislature, the PM/Chancellor could also serve as the Speaker and run to the day-to-day legislature or it could be a separate position, perhaps elected by the Governor.
The Northern Parliamentary Republic could be a fun idea but, on the other hand, I don't see why we need to break the mold on the regional government.
I was thinking a three man Senate and the rest, House of Representatives, just like what our upcoming Republic is. But the ideas presented are also worth a try.