She would pit in perfectly with the Angel Investigations gang. I always found it telling that her character was always able to truly shine on Angel.
Having a Slayer at your back would definitely make cases go a bit smoother, or with Slayer's luck draw the attention of a Big Bad.
I also think that colleagues like Wesley, Gunn, Fred, Illyria, and Spike (characters who all have a darkness) would do a great deal of good for Faith. They could all relate to her darkness a hell of a lot more than the Scoobies ever could.
I could accept Faith as a love interest for Angel as long as it was taken slow and developed carefully over time. I always saw the potential for something more between the characters, but it would suck if it jeopardized the friendship and chemisty they already have. If Faith stayed in LA after the Angelus arc, I could see Angel become closer to Faith since that season was filled with Wacko!Cordy.
I would definitely like to see Buffy's reaction if Angel and Faith ever got together. You thought she was bad in Sanctuary...? Oh boy!
I don't think there would be a chance in Hell that she would agree to work at Wolfram & Hart, though. Not after all she has been through; after all she's done.