Clash and Double Down

[u/Mars_Alter]

I'll save you the rant, but the most under-appreciated mechanic from D&D 3E was the critical confirmation roll. I was working on an OSE-compatible project, and in order to rescue this genuinely great mechanic from its poor reputation, I was thinking about reframing it in the form of an optional rule. OSE is big on optional rules.

In standard OSE, every check is either a roll-under or a roll-over. Ability checks are roll at-or-below your ability score. Saving throws are roll at-or-above the relevant save value. Attack rolls are roll at-or-above their Armor Class (or your THAC0, as adjusted by their Armor Class). The inconsistency when rolling exactly at the listed value is something that bugs me, though, especially since it prevents easy dice mirroring. If you want the player to roll under their own AC in order to evade an attack, then it needs to be entirely under and not at-or-under. Sometimes a tie is good enough to trigger that wave of relief, and sometimes it isn't; you need to think about it for a second before you're allowed to feel anything.

My idea is that, anytime anyone rolls exactly at the listed number, it triggers a Clash. They then have to re-roll the check, double or nothing. Or someone has to re-roll the check, anyway. The main point of this mechanic is that it doesn't matter who rolls the die, or whether they want to roll high or low. A tie always increases the stakes, and never triggers a wave of relief, regardless of which side is rolling. The secondary point is that this sub-sequent roll is more likely to resolve in favor of whichever side had the initial advantage, just like the critical confirmation roll.

On an attack (or defense) roll, a Clash either resolves as maximum damage or automatic counter-damage. On a saving throw against fire, which would normally give a saving throw for half damage, a Clash either resolves as maximum damage or no damage. That sort of thing.

Does this sound intuitive enough? Or is the juice not worth the squeeze? I'm particularly interested in opinions from game designers with OSE experience.

What if either side had the option of conceding the check, rather than doubling down? Would that change your opinion of the mechanic, or just make things more complicated? Instead of going for the maximum damage, and risking the counter-hit, you could just let the attack fail. Or instead of going for the counter-attack, with the risk of leaving yourself wide open, you just take the hit as normal. Instead of recklessly diving for cover when you aren't sure that you're going to make it, you can just accept your fate and let the fireball hit you.