Id settle for 3. 1 in the north, 1 in the center, and 1 in the south: Gwynedd, Powys, and Deheubarth. Think about the gaming applications instead of the historical/realistic ones. It was only Deheubarth and Gwynedd that mattered to the Normans as far as organized resistance. Those two princes were the only ones with resources enough to oppose the crown, the ones who led the rebellions, the ones who recaptured territory during the Anarchy, the ones who signed the treaties, and the ones who entered into vassal/ally relationships with the English king. And when there was a campaign, those two were the ultimate targets.
After 1066, the rest of Wales was gradually subjugated by the Normans. The Earl of Gloucester held the Lordship of Glamorgan, the Clares ruled Pembroke and Gwent, The Earl of Cheshire had pushed into Flint and beyond, and in the center, even after the fall of the Earls of Shropshire, the lesser marcher barons were building castles as fast as they could. And when Henry I died and it was time for resurgence, who started knocking off English castles right and left and reclaiming Cardigan and so on? Gwynedd & Deheubarth.
Like yourself, Id be disappointed to see just a one-province Wales. So if I had to pick, its Gwynedd & Deheubarth that MUST be included as separate entities.
