User blog comment:BlackWizardZeref/Fairy Tail Chapter 394: Juvia vs Keith Review/@comment-77.194.131.94-20140727112004/@comment-25244540-20140727160921

You're forgetting Franmalth wasn't aware that Natsu and the others defeated him. Check Chapter 375 cause he goes "Eh?" when Natsu tells him that they beat Hades.

Going by that fact alone, I don't think he gains the knowledge because he doesn't have the memories of how they fully used their powers. Franmalth relied on his curse more than Hades' magic.

Plus even if Franmalth gets the chairman's magic, does he even know how to actually use it? That would be the main issue going by what I just stated above.