Is it right that when WP decided to leave and Grissom left the lab, Ray kinda got an overhaul? I found an interview in one of the magazines that was specifically about Warrick leaving but said they were looking for " a male series regular in his late 20s to early 30s play 'Ray Santoro', a handsome, smart and athletic CSI who transfers from Henderson to join the graveyard shift at the Las Vegas crimelab."
It seems to me that they had the idea for Ray, but then when WP announced his departure, they kinda had to scramble and rewrite Ray to accommodate a bigger star to fill WP's spot...getting LF would have made them have to make Ray older and a bit less athletic, although I think the handsome part is still there pretty much. They must have felt they needed to give him a different background...I think the professor thing fit him a little better in the end. We do already know they had to rewrite the 'serial killer gene' thing, although it's still there in its current form, but I hadn't realized this part.
I do wonder why they altered their target from a younger guy though, if that was due to hiring LF or a decision due to WP's departure that ultimately led them to choose LF as their star. IDK if they could have made it work with a younger big star or not. *shrug*