Isn't martial arts from Ja2 a perk or a trait aka a perk you get from the start rather than leveling up? A mercenary with 100 Dex and Str won't be able to do Kung fu without It while a mercenary with lower stats can because has the trait. This was introduced in Ja2, in Ja1 you didn't have combat perks but traits were Psycho, blind and forgetful.