I looked closer at the code.
For the S&W Revolver the amount of damage a weapon does is stored in function RevolverImage::damage(%this, %obj, %col, %position, %normal)
That function does some checks on where it's hitting, and then triggers %col.damage(%obj, %position, %damage, %damageType);
I need to catch the input of %col.damage
I shouldn't replace %col with the brick ID and create a fxDTSBrick::Damage function as if the revolver did a check such as %col.isCrouched() it would throw an error.
I could create a bot, and package up AIPlayer::damage() so that it catches the amount of damage for me.
If I need to use this mod in the future, that is what I will try.