For non-damage stunts, I might try something like this:
Stunt
A maneuver that, if successful, confers an effect that is not an attack.
- Static Difficulty: 15
- Roll: d20 +Mod +Level
- Alternate Rule: d20 + Mod + Level if Mod is a Class Req (ie. STR for fighters)
- Levels of Success:
- minor: win the roll
- major: win the roll by 5
- critical: win the roll by 10
- Failure: on a miss of more than five, become exposed, next attack against rolls 2 dice, choosing the better result.
Usage
A stunt replaces a move or an action.
Effects
- minor: a small, situational or positional gain
- major: on next action, roll two dice and take the greater result.
- critical: as major + next action against rolls two dice and takes lesser result.
Replace or bolster the above with contextual advantages as befits the situation.