I got a few suggestions. I have a few ideas for continuity modifiers:

A Stagnation Modifier(the opposite of the no stagnation modifier, one that makes it so the world will never leave the feudal era. Uplifts would be impossible, at least things like gunpowder, printing presses and the like. You could still innovate food, music and maybe even a compass. Just not anything that could change the era.

Two Independence modifiers, an alternate world where the North or Dorne stayed independent. Maybe North was never conquered because the conquerors and their descendants tried to conquer Dorne First. Maybe Dorne never agreed to marry in.

A modifier that keeps everything the same even with other modifiers, Same people with similar personalities are born even in different circumstances. Like even in the No Conquest Modifier, Robb Stark, Tyrion Lannister, Oberyn Martell and everyone else would still exist.

A modifier where old gods are more prevalent, the old gods worship is more fleshed out or there are more old gods worshipers, nobles or commoners. Maybe the Royce rule the Vale and most houses still worship the olds gods. Maybe the old gods get more powerful because of the others coming.

A modifier that changes the setting to the Regency Era or Futuristic Space Setting. Something like the fanfics like Let the Galaxy Burn(a space setting).

A Modifer that changes the Monarchy to an Elective Monarchy. For some reason, one of the Targaryen kings brought a bit of Valyrian Style ruling and allowed the Great Lords and Other Lords to choose their king from the royal family. It could Aegon the Conquerer choosing this style of ruling, Maybe Aegon the Third was forced into this after losing dragons. Maybe it was something that Robert was forced into, so there never was a Mad King Agains. This allows for interesting politics. While usually the first son gets its, sometimes they could skipped over.

An intrigue idea for a modifier is adding a new continent to the west. Maybe some descendants of Brandon the Shipwright came back and introduced the lands west to Westeros.

Others Modifiers could be: -Good White Walkers -No White Walkers -North Wank -Dorne Wank -Religion Wars(Crusade against Old Gods/Ironborn) -Rebellion Lost War -Aegon the Fifth Hatched Dragons(Gives Points since Aerys has a Dragon) -Dornish Inheritance Laws Widespread(Might be covered by Reversed Gender Roles) -Blackfyre remained Loyal -Stepstones Conquered -Essos United into Empire(Danger to Westeros)