Already done that.
Not exactly dislike, I meant the players would probably come to like the gruff old detective dude more. Without giving too much away of the plot, if the player has started to relate to the protagonist, he'll be in for a kick in the balls at the end, Silent Hill 2-style.
By the way, I gave this lady friend a thorough plot synopsis with a psychological analysis of the main character, and she went 'Fuck yeah, count me in. She sounds like a batshit insane character, I can identify with that."
(If this project actually gets finished, I'll probably ask her to do some voice acting too.)