Current touch attack AB implementation on Arkhalia:

BAB + size modifier + ability modifier if higher than 0 + nature sense (in nature areas only) + bane of enemies (against favored enemies only) + epic prowess feat + normal/greater/epic weapon focus (spells) + point blank shot (ranged only and within 5meters) + “effects”

Ability modifier for melee “touch attack”
Strenght modifier or dexterity with weapon finesse (if its higher than Strength)
wisdom with intuitive attack (if its higher than strength)

ability modifier for “ranged touch attack”
dexterity mod
wisdom mod with zen archery (if its higher than dex)

“effects”
are “capped” bonuses to attack bonus from spells like bless and activable feats like bard song
+ iouns
+ legendary levels ( Ranged or melee attack bonus depending if its melee or ranged touch attack)