-Hp +Spd Cain?

He's a good Brave Sword user, with those IVs I think he can quad.

Despite this question being for actually using Cain, I would maybe suggest feeding WoM to a nuker? Like a +spd Blarblade Mae or Nino with breath of life. That's how I have my Mae set up (not +spd though). +Atk, Blarblade, LaD3, and Breath of Life 3 along with the seal. I used that build for the Tempest during the Path of Radiance theme but I've found other uses for it as well.
But to answer your question, it really isn't worth the fodder. Sure, taking his brave sword away and giving him fury would result in 38 speed, but all the skills you gave to him can be used to build other and better units. I think it's for the best that he stays WoM fodder.