Yes, I have. But it's a bit complicated.
First, establish the character's Sanity, Stamina, and skill points.
Calculate your Imbalance Bonus:
18 minus [half the sum of the Sanity and Stamina], minus [Sanity or Stamina, whichever's lower].
For a typical character, this will range from -2 (for a 10/10) to 2 (for a 14/6 or 6/14) .
Next, list off the character's stats, and apply these modifications:
Dexterity times 5/4
Intellect times 3/4
Willpower times 3/2
Lore times 1/2
Luck times Skill tokens divided by 3
Your luck should be 1 to 5, and your other stats should be 2 to 8. Try not to go outside those bounds.
So, the next part would be to give the character an ability and an item (or spell). Each item and ability has a "power" value between -2 (not very good) and 2 (quite useful). Unfortunately, since this is subjective, the best I can do is list examples of what consider to be different strengths, and you can compare your ideas against them:
- Power 2: Camera, Shrivelling, Tommy Gun
- Power 1: Duke, Walther Model 9, .45 Automatic, Dynamite, Revolver, Studies on Hysteria, Necronomicon, Cult Robes, Warding Statue, Isabel's Letter, Magnifying Glass
- Power 0: Plague of Locusts, Flux Stabilizer, Holy Rosary, Sword Cane, Whiskey, Bone Saw
- Power -1: Blood Pact, Mists of Releh, Soul Pact, Gray's Anatomy, Typewriter, Holy Water
- Power -2: Bind Monster, Guitar, Flash Powder, Microscope
- Power 2: Hypnosis
- Power 1: Disappearing Act, It's Personal, Find Weakness, Autopsy
- Power 0: False Trial, Detail-Oriented, Professor's Instinct, Master of Illusion, Psychic Sensitivity, Trial and Error, Not a Scratch, Solace In Prayer, Field Medic
- Power -1: Powerful Visions, Holy Warding, Jury-Rigging, Unwavering Determination, On the Case
- Power -2: Intervention, Keen Eye
Bear in mind that if your items and abilities play off of your characters' stats, you should take that into consideration. Something that gets stronger with more skill tokens, for example, should not give a good power score if your character doesn't start with many.
Finally, sum the above values and add them to your Imbalance Bonus. Your target value is between 32.5 and 33.5. So, just adjust your stats as appropriate until they fall within the target range.
Please note that this ruleset, when applied to official characters, will not necessarily result in their abilities falling in the target range, but that speaks more to how I feel the characters are imbalanced. The above technique was the basis for my character rebalance project, where I aimed to both rebalance the characters' stats, and make them more like their Arkham counterparts.