This seems to refer to this article about how the new skill inheritance system might let you pass certain tomes (which is the attack skill and is therefore normally not inheritable, especially not a unique one) around, specifically, replacing Leo's Brynhilde with Nino's Gronnblade+.
(Also, Leo's Brynhilde is a divine weapon with serious plot significance in Fates, signifying Leo's heroism, and is equivalent to Takumi's Fujin Yumi, so he has no intention of giving it up... even though in Heroes, it really sucks, and just does a support debuff lowering mobility after dealing damage when a unit like him should really be gunning for the kill. Gronnblade+ deals extra damage based upon buffs.)
Update: Holy shit, this works way too well. Seriously, WTF, Intelligent Systems?! You seriously let there be an uncapped 1:1 boost to attack just for holding a Gronnblade?
I did this with Cecilia, and had Gunter and Jagen give their +6 to all stats buffs to her, and she was dealing between 50 and 80 damage in a shot. (I then gave her Darting Blow to help make sure she gets double strikes, and Desperation so that both shots go first, basically guaranteeing first strike kills even against reds.)
Takumi is total roadkill at this point, but arena matches are even more games of rocket tag than they already were.
Furthermore, eat a bag of dicks, Takumi. I swear, he's in 80% of all high-tier teams, and at least 10% of them have TWO Takumis. Granted, now having three characters that can first-strike him (and the fourth practically being a support at this point), I've lost all fear for him, but still, use a little variety, you know? There's a reason nobody uses any flier that isn't Camilla.