The way I see it he's a honey trap no matter the outcome. Even if he stays as a spawn he says Cazador is and always will be a part of him. Maybe in a few years down the line he starts regretting his decision and blames Tav for influencing him and turns into an angry and bitter monster? He might also find other ways to empower himself.
After abandoning the ritual he thanks Tav and says all sorts of nice things. But that's what he does - he knows what to say to others to make them feel good about themselves. Frankly, I wouldn't be amazed if he actually prepared that monologue for Tav for the occasion (Shadowheart catches him rehearse compliments once). In his spawn ending he lies to Tav that he'd be ok if they wanted to part ways.
