Throwing in my own two cents here.
'If the confirmation roll is a miss, then your hit is just a regular hit.'
I think this bit here would supersedes the misfire rules given that even if you do rule that a gun could misfire (an automatic miss, yes?) on a confirmation roll, this bolded part here would just circle it around again and rule it as a regular hit in the end. So just like a normal failed confirmation roll.
Besides, why would you want to punish a player for failing a crit of all things?