Here’s an idea. What if the character’s importance in the story dictated what they could affect in an action?
If your game has main characters (PCs and primary villains) and supporting characters (companions/allies and minions), as a character takes “plot damage” they are reduced in importance. Main characters are reduced to supporting characters and supporting characters are removed from the story.
Translating this to mechanics, main characters could be capable of affecting the story (changing the narrative by attacking enemies, placing advantages/changing the environment, etc.), while supporting characters are only capable of aiding the actions of a main character (combining skills in teamwork actions, etc.). And a character who is removed from a scene loses all agency.
Narrative damage could be akin to advantages in Fate, or complications in Cortex+. There could even be a mechanic to move up and down in narrative importance, like overcoming/removing a complication or enemy-placed advantage. Or, if a main character supports a supporting character in some way (healing, doing a favor, etc.) they are lending some of their importance to the supporting character, thus returning them to main characters (if they are capable of that level to begin with).
Taking a Fate fractal approach, supporting characters could also be represented by weapons. They are supporting of the character, and thus not capable of affecting change. They can, however, use their “skills” to modify their wielders, and may possess special abilities to further enhance a character.
Another way to mess with supporting characters is to treat them like an environment. A simple overcome action will remove them completely from a scene.
This may oversimplify game mechanics (or confuse them, depending on the game this is being applied to), but the idea of narrative importance is fun to play with, and it isn’t new. The Wushu RPG uses narrative importance a lot, but characters don’t move between levels of it. But maybe they should? I could see a Wushu character being reduced to a supporting character (passive minion or spending some of their dice to make additional descriptions for their allies) when they run out of Chi.
I don’t think I’ll use this mechanic anytime soon, but it was a fun idea that hit me, so I’m hitting you with it. (You should put some ice on that.)