Wait a minute--what should these new Character Sheets look like? Didn't I already DO a character sheet? I really have to do another one?
No, you don't. Let's use Flagg as an example: Say he loves his crazy Leos, and who doesn't, so Flagg wants to continue using Leos. He can do so without tweaking his CS at all. Just let the GMs know, get our okay, and there you go.
But what if I want to do a new House/character? Or if I just want to do a new CS?
That's absolutely cool. In that case, I'd suggest one to two paragraphs for personality and bio and...you're done.
As an example, the Aegon CS:
House: Targaryen of Dragonstone
Name: Aegon
Age: 30
Personality:
Aegon was seen as an enigma. He was a solitary person whose only friend was Orys Baratheon. He was a great warrior who wielded a sword called Blackfyre but only rode his dragon for battle or travel and never entered tourneys. He remained faithful to his sisters and left governance in their hands and only took command when necessary. While he was harsh with those who defied him, he was generous to those that bent the knee.
Biography:
Aegon was from the island of Dragonstone, the westernmost outpost of the Valyrian Freehold, which his family had settled over a century before the Doom of Valyria. According to Targaryen tradition, Aegon married within the family; however, instead of just one sister, he married both of them: his elder sister, Visenya, and his younger sister, Rhaenys. All three were dragon-riders before they were wed.
When Aegon was quite young, Volantis inquired whether Aegon and his dragons would join them in the east in a grand alliance against the other Free Cities, remnants of the Valyrian Freehold. He apparently rejected the offer. When Volantis invaded Tyrosh Aegon came upon his dragon Balerion the Black Dread joining the Storm King and Pentos on the side of Tyrosh instead. After the defeat of Volantis, Aegon returned to Dragonstone.
...and that's it. Labor intensive, right?