Download The Jack 2.0 here.
The original writeup for the Jack was a prototype - it included several ideas I was working on, including streamlined thief skills, point buy for thieves, and thief/warrior/wizard multiclassing.
I designed the original class with the intention that it would be just as competent as the Warrior or Wizard classes if all points were spent specializing along those lines. I realized afterward that this conflicts with one of the basic assumptions of DCC - role protection.
DCC is balanced not through careful weighing of class powers, one against another. DCC is balanced through randomization, high lethality, and role protection. The Warrior has mighty deeds, the Wizard has wizard spells, spellburn, and patrons, the Cleric has the cleric spell list, divine aid, and disapproval, and the thief has the luck die and thief skills. Each class can do something amazing that the other classes simply can't.
So, if you are going to create a Jack-of-all-Trades class that can mimic the key features of other classes, you need to make the new class perform substantially worse when doing so. Mighty Deeds without the damage bonus and requiring luck burn. Unreliable shared luck. Caps on spellchecks and types of spells available. That sort of thing.
Something worth mentioning: when I was going through the spell list from the Rulebook, trying to isolate those spells that allow wizards to exponentially increase their power over time, I came up with the idea of Ritual Magic, defined as any spell requiring a turn or more to cast. This includes spells that allow for permanent increases in future spellchecks, the creation of magic items, the summoning of permanent or long-lasting servants, and Patron Bond. Restricting access to these spells is an excellent way to secure the position of Wizards as the primary spellcasters in the game.