Transforming a bro like Brint to get a near perfect moowife like Brienne is like some sick monkey's paw wish. Wsan thinks giving the cursed armor to Brint to turn him into Brienne is alright because The Champion has no idea what the armor will do, but you the player know that even though Brienne still retains her memories as Brint she's pretty much a different person entirely. Brint is gone so you could get your cow wife. I can't believe I'm saying this, but Tobs is sort of right in that the choice to tf Brint is pretty much out of your self interest.
tl;dr : Just separate the two for crying out loud