The Anglo-Norman Empire under Richard II, called 'the Great' (ongoing game)
William the Conqueror not only gained a kingdom, but also a new enemy as the Scots tried to install the House of Wessex as kings of England. After he fell in battle against the Scottish king, his second son Richard (Robert died as a child) crushed the Scots and the Northern uprising led by the lords of House Hwicce - who were subsequently banished, together with the other rebels, and lost everything their family possessed. Lancaster and York were given to Norman Nobles. After Northumberland was inherited by a Scottish noble, Richard crushed the Scots (again) and retook it for the English crown before looking southwards. After gaining the Approval of the pope and an stable alliance with the emperor, Richard invaded France.
The Capets surrendered after almost the whole North was occupied and Richard accepted their submission - leaving them and the Southern lords in their positions at power, an error which would haunt his house for decades. The Capets continued to hold several duchies in the North while the houses of Toulouse and Poitou ruled over two thirds of the South. Richard, now known as 'the Conqueror' (these Normans were a creative bunch), united his lands unter the English crown, thus further upsetting his Southern vassals. While he continued to rule directly over England and Northern France, its noble now mostly Normans, he appointed a regent to rule the South in his stead. After finally consolidating his rule in France, he expaned into the Mediterranean Sea, establishing trade ports on Corsica, Sardinia and the Baleares. He also conquered Murcia and Granada from the Muslims, but instead of making it part of his empire, he installed a Norman as independent king of Murcia - whose dynasty would later on inherit the throne of Castille and unite half of Iberia, thus expanding the Norman sphere of influence. His efforts to concentrate power in as few positions as possible led to the permanent unification of Lancaster an Northumbria under one ruler, thus making the North easier to control. Richard I's rule was one of greatness and prosperity - before he was murdered at the age of 71, presumable for being a massive dick.
His son, William, was more a administrator than a conqueror and not nearly as powerful as his father. As soon as his father did his last breath, the whole South was in rebellion. The regent Richard originally installed was usurped by his sister, who, despite being married to William's firstborn, declared herself queen and rallied the discontent lords around her. His father would have crushed the rebellion but Richard I wasn't only a good fighter he also had ties to the Imperial family - ties his son failed to strenghten. The rebellion lasted for 4 days and ended when 'Queen' Sybilla I fell down some stairs. She died childless and her brother, the old regent, was grateful to William for regaining his position and William's son - who would later follow him as Richard II - married a Capet to strenghten the former royal dynasty's ties to their new overlords. After pacifying the South, another problem arose in the North. The king's cousin whose ancestor was tasked by William the Conquerer with ruling his old lands, followed the example of the lords of Lancaster and subjugated the always rebellious lords in Flanders and the nobles of Anjou, unifying the Northern coast under his rule. The king of England and the dukes of Normandy were never on good terms due to the latter's claim to the crown. The unification of their lands gave them a solid power base, should they ever try to claim the throne. To avoid another self-proclaimed king rebelling, William tried to appease his cousin and, if that didn't help, outright threatened him. Under his rule, the Provence and Dauphiné, formerly disputed by the Bosonids, the emperor and Williams aunt, wife of the Swedish king, were put under English rule. He died peacefully and though he had murdered and threatened ambitious vassals, he was remembered as William the Just, for he did not resort to outright banishment of whole families like his father did.
Richard II followed him on the throne and furthered the centralization process his grandfather initiated by installing regents in Burgundy and the Provence. Under his rule the trade republic of Genoa was forcibly dissolved and the city became a part of the Provence. He also invited a Roscelin de Hauteville, former duke of Apulia, to England and appointed him as new Southern regent after the old regent died without issue. Richard II plans to use Roscelin's dynastic ties to claim Sicily for England and finally earn the title his subjects already associatie with him - 'the Great'.
The game isn't finished yet, but until now it was very interesting. The idea to build a lasting Anglo-French empire came up when I've seen William rule both kingdoms in another save game. I've not even tried to conquer Wales or Scotland because I wanted to concentrate on holding my French holding together - and as far as I remember, the fortification of Wales alone ruined the English kings and weakened their position - something I want to avoid, RP-wise. I also don't want to deal with the Celts constantly rebelling. Maybe I'll annex the rest of the Isles and replace every noble with Normans/Englishmen after being finished in Sicily.
England is at the moment a mix of Normans, Anglo-Saxons and English, with my kings still being Norman despite ruling from London. Maybe I'll stay Norman to keep the major part of my vassals - the French ones - in line.
Additionally, I'm not roleplaying my ruler as an emperor. He might ruler over an empire territory-wise, but he's "just" a king. His king-tier vassals are hereditary regents, nobles who are appointed by the king to rule over parts of his kingdom in his stead. Only if they rebel against me, I'll consider them kings. The current regents are:
Stephen I de Lindisfarne, Hereditary Regent of the Northern provinces (Lancaster, Northumbria, maybe I'll give him York later on)
Faramond I de Normandie, Hereditary Regent of the Normandy (Normandy, Flanders, Anjou)
Roscelin I de Hauteville, Hereditary Regent of the Aquitaine
Ava d'Avaugour, Hereditary Regent of Burgundy (Bourgogne, Dauphiné)
Aléarde I de Châtillon, Hereditary Regent of the Provence (Provence, Genoa)
Gervas I Roger, Elected Regent of Mallorca and Sardinia (Mallorca, Sardinia/Corsica, this one is a trade republic)
I'm currently thinking of changing my name, but until I'm coming up with something better, I will keep 'England'.