I would just have it as a simple trigger, probably on an Interceptor.
"You may change an evade to a blank, gain an evade token".
- Works while stressed,
- Taking an evade helps it a bit,
- Can be used repeatedly so useful against focused fire,
- Doesn't last till next turn because thats a pretty powerful effect,
- Penalises opponents for taking potshots,
- Combos synergistically with stealth device (which is all but extinct these days),
- Isn't fixed to having to roll more evades than hits makes it simpler,
- Possibly too abusable as an EPT.
It's an interesting idea, but as an ability it is a bit luck dependant too, since it is almost always better to prevent damage now that wait till later (gunner is one exception).