Power Fists, Dark Blades, Eviscerators, Furious Charge, Great Weapons, Combat Drugs, and Strength enhancing weapons/gear are fine- they alter the strength of the initial hit, not the penetration.
The 'Doubling scores' in the FAQ refers to Ork Super Stikk Bombs, because they doubled the result of the D6 before adding strength when penetrating i.e Str + (D6 x 2). Before the FAQ, Orks were capable of decimating Monoliths because of this 'doubling bonus', whilst every other race was penalized. The quoted wording is to clear this up, but as usual, GW isn't thorough enough to state this themselves. Also remember, this FAQ was before the RAW era
Hence, 'Fists and Strength enhancing weaponry and gear is allowed, because it is still only Strength + single D6, the original intention of the Living Armour rule.