Damage house rule... What do [i]you[/i] think?

Hello,

today I came up with the following short house rule for CAH.
I think it enhances the games that I would like to run,
and I am seriously planning to keep it as a house rule on
the Iconia play-by-post group.

The rule is:

Rolling a "12" with Stunt Points:

Whenever somebody rolls a natural die roll result of "12" in
a check for any of the three Combat traits, not only do you
add in your own Oomph stat to the die roll+trait rating, but
also to the following damage roll.
Now, if the result of "12" was achieved in a trait check to
which you also added your Oomph by spending at least one
Stunt Point (!), the Oomph score is added once to whatever
damage roll you get next, but that total damage result will
also automatically bypass any armor, real or magical.
The Protection value of the opponent affected does not help.

Example:

Joey uses his Armed Combat trait (4) against a chief villain...
He gets a die roll result of 12, but the player also declared in
advance that he wanted to spend two Stunt Points on this
action -- to ensure a high total --, and Joey has Oomph 3.
So, the total for this trait check is 12+4+3+(2 x 3) = 25.
This beats the villain's Athletics result, so Joey is entitled to
a damage die roll next. His club inflicts DR 5+Body (2).
The damage die comes up "6".
So, the damage total is, 6+5+2 (for Body) +3 (for Oomph) = 16.
These 16 points automatically go through the villain's armor,
and thus have to be subtracted directly from his Hurt Points.
This is only because Joey's player had declared in advance
that this was a Combat trait check with Stunt Points.

(That's the RuneQuest player in me wanting to use this rule.)

Q: Is that too complicated?