ITA about Wedges.
I think that part of the reason Sofia/Brass worked better for me than GSR, despite the mentor/mentee similarity was that the mentor aspect of Brass and Sofia's relationship never felt apparent in their dynamic. Sofia was a professional subordinate, but she and Brass never treated each other like one person was more important. Sofia stood up for herself a lot, and Brass treated her like the strong, independent woman that she was. They treated each other like equals, despite professional positions.
I don't mean this as an insult to GSR, but, IMO, with Sara and Grissom, it was always very apparent in their interactions that Grissom was in the position of power, especially in earlier seasons. I think it didn't help that Griss and Sara were both workaholics. Work was their life, so it makes sense that their professional positions would have greater bearings on their interpersonal relationships. They were, IMO, always the two characters that seemed to treat other characters, in general, the most differently based on position. Cath, for example, doesn't act that differently toward Greg than she does toward Grissom, but, with Sara, I always got the feeling that she knew she was above Greg and below Griss.
I can kind of see Cath/Brass just because they're both great characters. I think they would have very similar perspectives, having both already been through failed marriages. I can imagine they'd have some of the best, most hilarious conversations just because they're both such fun characters. That said, I'm still a Yo!Blinger at heart, so it's hard to see Cath with anyone else. But, if she were with someone other than Warrick, I think Brass would be a good candidate. I honestly think that they'd make each other happy. I think they'd be a really fun couple in general, which would be a nice departure from angsty romance on the show.