Planning to Hack Fighting Fantasy

The one trait, "Skill" is nearly all-encompassing for almost any activity in the game.  Feats of Strength, Agility, Intelligence, etc all covered by one stat.  Swinging a sword in battle is obviously an exercise in Strength and Agility (and often intelligence).  Picking a lock can require dexterity and intelligence. In my experience, lock picking requires luck.

For adventurers, this isn't entirely inappropriate.  If you're a skilled adventurer, you're bringing everything you got, your strength, your agility, your wisdom, your intelligence, your life experience, etc to bear.  The balance of all of that is your Skill.

How does one, then, create character classes for this game?

My first thought is to let a Thief burn luck (ala Dungeon Crawl Classics) without rolling to do any kind of thiefly activity.  Likewise a warrior can burn it to do damage or to hit in battle.  Luck testing could remain for involuntary tests like natural hazards, surprise attacks, etc.  

Or perhaps a better approach is to take the USR approach, disregard classes and have the player pick a few skills for his character, and give a bonus to the Skill stat for those activities.  I understand that Advanced Fighting Fantasy takes this approach.  The only drawback to that would be pushing a skill over 12.  How does one test that?  If you roll 12 on two dice, then roll one more die.  If the total is < or = to the skill, you succeed.  For example, you have total skill of 14 in picking locks.  You roll double 6's on the test, so you roll d6 <=2 to succeed. 

Perhaps you can cap Skill at 10, and allow bonuses to bring it to 12, and then require Roll Under (not equal to) to succeed.  

I've yet to receive the "Sorcery! Spell Book".  I don't know how to work magic into the game.  I considered creating a "Magic" stat and just roll 6+d6 for magic skill.  The other option is to create a points based system and let the player build the character.  

Here I am, a self described minimalist, considering all kinds of options.

Updated post.  If I convert skill checks into 2d6+skill vs a target number, then skills could exceed 12 without any problem.  In doing so, Fighting Fantasy becomes "Tunnels and Trolls" with fewer stats and less dice.  Throw in a little Old School Hack, and make the target number 2d6 + Difficulty. Say the standard difficulty being 7.  So 2d6 + skill > 2d6 + Difficulty = Success.