Weapon skills are almost all DX based, which makes sense to me. For most of them, I think allowing a Perk to base them on something else would be iffy. The character must control a weapon and maneuver it to hit a dodging opponent, or at least have sufficient arm coordination to punch the moving opponent in the jaw.
But in the case of Innate Attack, that dragon might be simply looking at someone and blowing fire, or that mage might be looking at someone and pointing a finger to cast a fireball. In these cases, Perception would seem to be primary over DX. Unless they suffer from a neurological or similar disorder, almost everyone can point at something successfully.
Consider this from
GURPS Power-Ups 2: Perks for Attribute Substitution:
DX-based skills with a complex technological aspect can shift to IQ (“Battlesuit based on IQ”), while those that involve fine work or hand-eye coordination can move to Per (“Driving based on Per”).
So do you agree with allowing Perk: Attribute Substitution (Innate Attack based on Per)?